研究者詳細 - 石川　健治

Quantification of Dangling Bonds Formed via Plasma Treatment as Reactive Sites for Functionalization of Hexagonal Boron Nitride Nanoparticles 査読有り Open Access

Inoue, K; Takagi, N; Ito, T; Shimizu, Y; Hakuta, Y; Ito, K; Ishikawa, K; Hori, M; Terashima, K

ACS APPLIED NANO MATERIALS 9 巻 ( 14 ) 頁： 6080 - 6089 2026年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Nano Materials

To elucidate the mechanism involved in the surface modification of hexagonal boron nitride (h-BN) via plasma treatment, we evaluated the number of reactive sites available for functionalization by quantifying the dangling bonds formed on h-BN particles during plasma treatment in solution. Electron spin resonance detected the boron dangling bonds formed on h-BN particles; these dangling bonds gradually decreased upon exposure to an atmospheric environment for up to 650 days as a result of oxygen termination, such as hydroxyl functionalization. These results indicated that plasma treatment increased the number of dangling bonds, up to 14-fold per unit mass, on h-BN surfaces as reactive sites for functionalization. The surface number density of boron dangling bonds as a function of air-exposure days could be expressed as Langmuir adsorption kinetics; the surface reactive-site density was estimated to be of 1015 m–2 on the plasma-treated h-BN. Polymer composite materials incorporating such functionalized h-BN after plasma treatment and oxygen termination showed markedly improved dispersion and flexibility. Overall, plasma treatment effectively introduced reactive sites even on chemically stable materials, while subsequent oxygen termination further promoted surface functionalization.

DOI： 10.1021/acsanm.5c05661

Preliminary study on the visualization and evaluation of non-thermal plasma dose profiles using radiochromic film 査読有り Open Access

Yasuda H., Kondo T., Ishikawa K.

European Physical Journal Plus 141 巻 ( 4 ) 2026年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：European Physical Journal Plus

Non-thermal plasma (NTP), also known as low-temperature plasma (LTP) or cold atmospheric plasma (CAP), has shown promise in cancer therapy and other biomedical applications, primarily through the generation of reactive oxygen and nitrogen species (RONS). However, the optimization of NTP-based treatments remains challenging because of the absence of standardized plasma dose units and practical methods for on-site dose profiling. In this study, we present a novel and simple approach for the visualization and measurement of NTP dose profiles using a currently available radiochromic film (Gafchromic EBT-XD) after removing a protective cover sheet. Clear radiochromic reactions were visible to the naked eye within seconds of helium-based NTP irradiation. The net optical density profiles of the RGB color components exhibited Gaussian distributions, with the red channel exhibiting the highest intensity. The X-ray equivalent doses derived from red channel optical densities reached approximately 40 Gy at the beam center for 10-s exposure at a distance of 8 mm or less and steeply declined at longer distances. The dose increased linearly with the irradiation time in the optimal dose range of the film (≤ 40 Gy). These findings demonstrate the effectiveness of this simple method for the rapid visualization of NTP beam and highlight its potential as a practical tool in biomedical applications including cancer treatment, enabling improved control and optimization of doses being delivered to patients.

DOI： 10.1140/epjp/s13360-026-07613-9

低温プラズマ技術の農業生産への活用に向けた取り組み査読有り Open Access

江原宏, 仲田（狩野）麻奈, 谷口光隆, Ahyuni Destieka, 杉浦史都, 黒澤生吹, 深澤満理奈, 中川万由子, 井上健一, 橋爪博司, 山川太嗣, 田中宏昌, 石川健治, 石橋勇志, 新田洋司, 二瓶直登, 菅波眞央

日本作物学会講演会要旨集 261 巻 ( 0 ) 頁： 219 - 219 2026年3月

Bactericidal properties of tryptophan and pyrrole solutions irradiated by oxygen radicals 査読有り Open Access

Kitagawa, D; Shimizu, K; Watanabe, T; Shimizu, M; Kato, M; Tanaka, H; Ishikawa, K; Hori, M; Ito, M

JAPANESE JOURNAL OF APPLIED PHYSICS 65 巻 ( 5 ) 2026年3月

Thermal-cyclic etching of SiGe with selective removal over Ge using fluorocarbon-based plasma and infrared heating 査読有り

Shinoda, K; Nguyen, TTN; Yokogawa, K; Izawa, M; Ishikawa, K; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 44 巻 ( 2 ) 2026年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology A Vacuum Surfaces and Films

Self-limiting thermal-cyclic etching of SiGe films demonstrating etch selectivity over Ge was achieved using alternating exposure to radicals generated in CHF<inf>3</inf>/N<inf>2</inf>/O<inf>2</inf> plasma and infrared heating. Si, Ge, and SiGe with Ge contents from 25% to 70% were used as sample materials. In situ x-ray photoelectron spectroscopy revealed a N 1s peak attributed to N-H bonds after radical exposure to SiGe and Ge. The peak disappeared upon heating to 100°C, indicating removal of the surface-modified layer. Cyclic etching of SiGe and Ge using a dry chemical removal tool shows thickness reduction with increasing cycles. The etch per cycle (EPC) for SiGe ranged from 3 to 7nm, while that for Ge was 1–2nm. Si was continuously etched. Saturation behavior with respect to radical exposure time was observed for both SiGe and Ge. Enhanced EPC of SiGe over Ge is attributed to the selective formation of the modified layer on SiGe surfaces.

DOI： 10.1116/6.0005128

Non-thermal plasma-activated methionine-containing Ringer's solution enhances cytotoxicity by increasing oxidative stress 査読有り

Fujisawa, K; Tanahashi, S; Katagiri, K; Takasu, S; Otsuka, T; Kamiya, T; Ishikawa, K; Esaka, Y; Hara, H

JOURNAL OF CLINICAL BIOCHEMISTRY AND NUTRITION 2026年2月

Formation of SCF+, SCF2+, and CS2+ ions during gas modulation cycles associated with interference between alternating C4F8 and SF6 in Ar plasma 査読有り Open Access

Yoshie, T; Nguyen, TT; Nguyen, TTN; Inoue, K; Tsutsumi, T; Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 65 巻 ( 3 ) 2026年2月

Photodissociation and electron-collision induced dissociation of C5H2F10 using photoelectron-photoion coincidence spectroscopy and quantum chemistry 査読有り国際誌 Open Access

Tran, NT; Hayashi, T; Iwayama, H; Ishikawa, K

SCIENTIFIC REPORTS 16 巻 ( 1 ) 頁： 5312 2026年1月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

The transition to high-aspect-ratio, eco-friendly plasma etching gases with low global warming potential (GWP) is critical for advancing sustainable semiconductor manufacturing. Hence, the dissociative photoionization dynamics of 1,1,1,2,2,3,4,5,5,5-decafluoropentane (C<inf>5</inf>H<inf>2</inf>F<inf>10</inf>), a promising alternative to conventional high-GWP perfluorocarbons, were comprehensively investigated. Fragmentation mechanisms were elucidated using an integrated approach combining synchrotron-based photoelectron–photoion coincidence (PEPICO) spectroscopy, electron-impact ionization mass spectrometry, and computational quantum chemistry. In addition to mapping the primary fragments (e.g., C<inf>4</inf>H<inf>2</inf>F<inf>7</inf>+, C<inf>3</inf>H<inf>2</inf>F<inf>5</inf>+, and CF<inf>3</inf>+), this study deciphered the complex rearrangement pathways leading to the prominent and persistent CHF<inf>2</inf>+ ion, which is a key species that cannot be formed by simple bond cleavage. Computational calculations revealed precise fluorine migration steps and energetic barriers, which were conclusively validated by the strong anticorrelation observed in the time-resolved ion yield curves. Exploration of the influence of electron energy on fragmentation demonstrated that lower energies (20 eV) preserve primary dissociation channels, whereas higher energies (70 eV) drive extensive fragmentation. This study provides a strategic framework for optimizing reactive-species fluxes in next-generation etching processes by linking tunable gas-phase dissociation, including controlled CHF<inf>2</inf>+ generation, under plasma-relevant conditions.

DOI： 10.1038/s41598-026-36140-x

Long-Term Dynamics of Nitric Oxide Radicals in Plasma-Activated Ringer's Lactate Solution 査読有り

Yamakawa, T; Inoue, K; Ishikawa, K; Hori, M; Tanaka, H

PLASMA PROCESSES AND POLYMERS 23 巻 ( 1 ) 2026年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

Medical applications of atmospheric pressure plasmas, including in cancer therapy, have attracted growing interest. Although ·NO in plasma-activated Ringer's lactate (PAL) solutions have been reported to exhibit selective cancer-killing effects, its radical dynamics during such treatments remains unclear due to the short lifetimes. The present study investigated the dynamics of ·NO in PAL solutions using electron spin resonance spectroscopy and fluorescence staining under varied plasma conditions. The results indicate the long-term generation of ·NO in PAL solutions over 6 h. The simultaneous presence of HNO<inf>2</inf>, H<inf>2</inf>O<inf>2</inf> and O<inf>3</inf> in that solution may play a crucial role in the generation of ·NO. These findings suggest that PAL solutions could function as sustainable ·NO sources, potentially enhancing the effectiveness of plasma-based therapies.

DOI： 10.1002/ppap.70122

Rice Seminar on the Utilization of Low-Temperature Plasma Technology under the JICA Knowledge Co-Creation Program 査読有り Open Access

Ehara Hiroshi, Kano-Nakata Mana, Tanaka Hiromasa, Hashizume Hiroshi, Ishikawa Kenji

Journal of International Cooperation for Agricultural Development 24 巻 ( 0 ) 頁： 2 - 4 2026年

Cycle etching of SiO2 film using Ar plasma irradiation of CHF3-condensed layer at cryogenic temperature below-120 °C 査読有り国際誌 Open Access

Sun, KD; Selvaraj, S; Hazumi, M; Hsiao, SN; Sekine, M; Abe, C; Sasaki, T; Hayashi, H; Ishikawa, K; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 64 巻 ( 12 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers

Cyclic etching is performed by injecting CHF<inf>3</inf> gas flow and irradiating with Ar plasma on SiO<inf>2</inf> films cooled to cryogenic temperatures below −120 °C. The etching depth of SiO<inf>2</inf> per cycle is maximized at approximately 4.0 nm by optimizing the thickness of the condensed CHF<inf>3</inf> layer through adjustments in CHF<inf>3</inf> injection time while keeping the etching time constant at 0.3 s. In situ ellipsometry successfully monitored the stratified layer thicknesses of the CHF<inf>3</inf> condensed layer and the underlying SiO<inf>2</inf> film in real time. This study demonstrates the feasibility of cyclic etching using CHF<inf>3</inf> injection and Ar plasma irradiation.

DOI： 10.35848/1347-4065/ae22ae

Formation of condensed CHF3 layer on SiO2 film at cryogenic temperatures for etching process applications 査読有り Open Access

Sun, KD; Selvaraj, S; Hazumi, M; Hsiao, SN; Sekine, M; Abe, C; Sasaki, T; Hayashi, H; Ishikawa, K; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 64 巻 ( 12 ) 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers

The etching rates of deep high-aspect-ratio (HAR) holes can be gradually reduced by increasing the HAR; this is called reactive ion etching lag. For SiO<inf>2</inf> etching at cryogenic temperature below −120 °C, condensation of trifluoromethane (CHF<inf>3</inf>) layers alternate with argon (Ar)-plasma irradiation was studied. An optical model of a CHF<inf>3</inf> condensed layer was constructed, and the condensed layer thickness increased linearly with CHF<inf>3</inf> gas flow rate and injection time. This behavior enabled the precise control of the condensed layer thickness and required a rapid switching between etching and condensation without any change in the substrate temperature.

DOI： 10.35848/1347-4065/ae20e2

Reaction surface analysis of plasma etching of SiN, SiO2, and poly-Si films using low-global warming potential CF3CHCF2 gas 査読有り

Tran, TN; Ishikawa, K

APPLIED SURFACE SCIENCE 710 巻頁： 163955 2025年11月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Controlling material selectivity in plasma etching is a critical challenge for next-generation semiconductor devices, particularly for achieving high etching rates while obtaining passivation-controlled sidewall shape profiles. In this study, the key reactive species generated in 1,1,3,3,3-pentafluoropropene (C<inf>3</inf>HF<inf>5</inf>) plasma are investigated, including etching ions (hydrofluorocarbons C<inf>2-3</inf>HF<inf>1,3-5</inf>+ and perfluorocarbons C<inf>2-3</inf>F<inf>3-5</inf>+) and passivating precursors. Their roles in the selective etching of silicon nitride (SiN), silicon dioxide (SiO<inf>2</inf>), and polysilicon (poly-Si) films are revealed by analyzing material-specific surface interactions governing the etching kinetics using integrated in situ quadrupole mass spectrometry and ex situ X-ray photoelectron spectroscopy. For SiO<inf>2</inf> surfaces, the high etching rate of 415 nm/min is driven by efficient fluorine flux from C<inf>2-3</inf>F<inf>3-5</inf>+ and C<inf>2-3</inf>HF<inf>1,3-5</inf>+ species. While, SiN surfaces exhibit a moderate etching rate of 290 nm/min, sustained by hydrogen supplied from C<inf>2-3</inf>HF<inf>1,3-5</inf>+ ions. Conversely, poly-Si surfaces show significantly reduced etching rates (<130 nm/min), attributed to carbonaceous passivation. By controlling the partial pressure of C<inf>3</inf>HF<inf>5</inf>, high selectivity ratios of SiO<inf>2</inf>/poly-Si and SiN/poly-Si are critically achieved for high-aspect ratio etching. These insights establish a universal plasma parameter optimization strategy for advancing selective etching processes for high-aspect ratio features in semiconductor devices.

DOI： 10.1016/j.apsusc.2025.163955

Revolutionizing reactive ion etching: ion-enhanced surface autocatalytic reactions enabling ultra-high throughput using cryogenic hydrogen-fluoride plasma 査読有り

Hsiao, SN; Imai, Y; Sekine, M; Suda, R; Iijima, Y; Kihara, Y; Ishikawa, K; Hori, M

CHEMICAL ENGINEERING JOURNAL 522 巻 2025年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemical Engineering Journal

Reactive ion etching (RIE) has been a foundation of semiconductor industry for the past 50 years, enabling the production of countless wafer everyday through its principle of synergistic reaction between chemical gases and ions. However, as device architectures advance, conventional RIE struggles with processing complex 3-dimensional structures with small features and high aspect ratios, leading to significantly reduced throughput due to the diminishing effectiveness of these synergistic reactions. This study demonstrates the transformative potential of plasma etching with hydrogen fluoride at cryogenic temperature, leveraging synergistic reactions between ions, physisorbed species and materials surface to dramatically enhance etching throughput. The co-adsorption of HF/H<inf>2</inf>O, confirmed by in situ Fourier transform infrared spectroscopy, on a cooled substrate results in a wet-like HF etching mechanism for SiO<inf>2</inf>, reducing the etching activation barrier to nearly zero. Unlike the linear dependence observed in conventional RIE, the etch rate under this approach exhibits an exponential increase with bias voltage, driven by the observed ion-enhanced surface autocatalytic reactions. This concerted mechanism demonstrates the promise of cryogenic plasma etching for enabling ultra-high throughput. Additionally, it supports sustainable development goals by eliminating the use of conventional fluorocarbon etching gases with high global warming potentials and addressing the need for energy conservation in semiconductor manufacturing.

DOI： 10.1016/j.cej.2025.167517

The Effect of Electrical Stimulation on the Cellular Response of Human Mesenchymal Stem Cells Grown on Silicon Carbide-Coated Carbon Nanowall Scaffolds 査読有り

Ono, K; Tanaka, A; Ishikawa, K; Takeuchi, W; Uehara, K; Yasuhara, S; Hori, M; Tanaka, H

BIOENGINEERING-BASEL 12 巻 ( 10 ) 2025年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Bioengineering

Silicon carbide (SiC)-coated carbon nanowalls (CNWs) have been proposed for use as implantable scaffold electrodes. Therefore, we investigated the effects of the SiC coating on CNWs and assessed the effects of the application of electrical stimulation (ES) on human mesenchymal stem cells cultured on SiC-coated CNWs. Measurements were conducted using immunofluorescence staining, proliferation assays, and quantitative reverse transcription polymerase chain reaction. Our results showed that the SiC coating increased the cell adhesion area, and the combination of the SiC coating and ES promoted cell proliferation. Furthermore, ES enhanced osteogenic differentiation on CNWs, both with and without the SiC coating. In SiC-coated samples, the increase in wall thickness of CNWs by the SiC coating promoted neural differentiation. These findings indicate that scaffold electrodes composed of SiC-coated CNWs enhance cell adhesion and proliferation; the application of ES to such electrodes promotes osteogenic differentiation, while the SiC coating itself promotes neural differentiation.

DOI： 10.3390/bioengineering12101073

Controlling etch selectivity of TiAlC and TiN films in nonhalogen N-H-O plasmas: Implications for DRAM peripheral transistor fabrication 査読有り

Nguyen, TTN; Shinoda, K; Miura, M; Maeda, K; Yokogawa, K; Izawa, M; Ishikawa, K; Hori, M

SURFACES AND INTERFACES 74 巻 2025年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surfaces and Interfaces

Titanium compounds, TiAlC and TiN, are work function metals and can be integrated into a 3D multilayer stacked structure of metal gates to optimize transistor threshold voltages in DRAM peripheral CMOS transistors. Selective dry etching of TiAlC and TiN is challenging, as both produce similar volatile products with halogen-based etchants. This study explores the etching behavior and selectivity control of TiAlC and TiN using nonhalogen N-H-O plasmas by analyzing their plasma-surface interactions with the transition from single-gas to mixed-gas plasmas. A capacitively coupled plasma etcher generated N<inf>2</inf>/H<inf>2</inf>/O<inf>2</inf> plasmas containing reactive species such as N, H, O, NH, NO, and OH, enabling selective modifications of metal compound surface at room temperature. The roles of N-, H-, and O-based species and the etchant composition in plasma-surface reactions were investigated through optical emission spectroscopy, in situ spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. The findings highlight the critical role of N-based species from plasma reacting with TiAlC and TiN surfaces to form C-N, N-H, and N-O bonds, producing more volatile products and enhancing the etch rate (ER). While adding O<inf>2</inf> gas to N<inf>2</inf>/H<inf>2</inf> plasma could enhance the selectivity (TiAlC/TiN), it reduced the ER. The typical bonds of the low boiling-point products selectively formed by the reactions of TiAlC surface with N<inf>2</inf>/H<inf>2</inf>/O<inf>2</inf> plasmas are proposed to be Al-CH<inf>3</inf>, Ti(Al)-N-(CH<inf>3</inf>)<inf>2</inf>, and Ti(Al)-O-C<inf>n</inf>H<inf>2n+1</inf>. Ternary etching diagrams for various N<inf>2</inf>/H<inf>2</inf>/O<inf>2</inf> ratios were constructed, offering a framework to better understand etching mechanisms and develop a method for the selective etching of metals and metal compounds with nonhalogen etchants.

DOI： 10.1016/j.surfin.2025.107664

Platinum nanoparticle-decorated carbon nanowall anodes fabricated via top-down approach for abiotic glucose fuel cells 査読有り

Sakai, R; Ishikawa, K; Kondo, H; Niitsu, K; Hiramatsu, M; Tanaka, H; Hori, M

SCIENTIFIC REPORTS 15 巻 ( 1 ) 頁： 32772 2025年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

A glucose fuel cell (GFC) was fabricated using abiotic catalysts supported on carbon nanowalls (CNWs) as the anode electrode. The CNWs were immobilized on a 50 nm-thick patterned Pt thin film and selectively grown on the unmasked regions of heat-resistant spin-on-glass (SOG) films. They were vertically aligned and uniformly spaced at approximately 150 nm through radical injection plasma-enhanced chemical vapor deposition (RI-PECVD) at 650 °C. The top and side surfaces of the CNWs, serving as electrically conductive supports, were fully decorated with platinum nanoparticles (PtNPs) averaging 1.8 nm in diameter. This decoration was achieved via supercritical fluid chemical deposition (SFCD) using trimethyl(methylcyclopentadienyl)platinum(IV) [(CH₃C₅H₄)Pt(CH₃)₃] as the precursor at 175 °C under a CO₂ pressure of 10 MPa. After etching the SOG films with buffered hydrogen fluoride (BHF) solution, the PtNP-supported CNWs (PtNP/CNWs) were lifted from the masked regions. This method provides a straightforward approach for GFC fabrication. The GFC, incorporating top-down-fabricated PtNP/CNWs as the anode and a carbon nanotube-based cathode, achieved a maximum power density of 25.3 nW/cm².

DOI： 10.1038/s41598-025-17364-9

プラズマ照射による植物の発芽および成長への影響査読有り Open Access

中川万由子, 井上健一, 仲田(狩野) 麻奈, 三屋史朗, 石川健治, 江原宏, 谷口光隆

日本作物学会講演会要旨集 260 巻 ( 0 ) 頁： 75 - 75 2025年9月

Selective etching of GaN over AlGaN through low-damage AlGaN surface processing at high temperatures 査読有り

Nakamura, S; Tanide, A; Ishikawa, K

JOURNAL OF APPLIED PHYSICS 138 巻 ( 5 ) 頁： 055701 2025年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

In this study, low-damage selective etching of GaN over Al<inf>0.24</inf>Ga<inf>0.76</inf>N was achieved using O<inf>2</inf>-added Cl<inf>2</inf> plasma at a high substrate temperature of 400 °C. Specifically, etching using 7% O<inf>2</inf>-added Cl<inf>2</inf> plasma at a bias voltage of 57 V achieved an etching selectivity of 14. Etching inhibition on the AlGaN surface was evaluated using in situ x-ray photoelectron spectroscopy, which revealed that Ga-O-N bonds formed at high temperatures selectively halted etching, differing from the Al-O-bond-based inhibition observed at 25 °C. This high-temperature process mitigates plasma-induced damage, preserving the photoluminescence intensity of near-band-edge emissions in AlGaN.

DOI： 10.1063/5.0259075

Atomically self-limited removal of Cl2-plasma-modified GaN by F2-added Ar plasma at high temperature of 300 °C 査読有り

Tanide, A; Nakamura, S; Jia, H; Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 64 巻 ( 7 ) 頁： 07SP9 2025年7月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers

Cycle processes of chlorine plasma modification and F<inf>2</inf>-added Ar plasma removal at a high wafer temperature of 300 °C was examined for self-limited atomic layer etching (ALE) of GaN. The threshold ion energy for etching of GaN by the F<inf>2</inf>-added Ar plasma was identified at high temperatures and found to decrease with increasing wafer temperature, ultimately reaching 23 eV at 400 °C, despite the low volatility of gallium fluoride. By selecting a wafer temperature of 300 °C and an ion energy of 57 eV, which is equivalent to the threshold energy, ideal self-limited ALE was achieved by combining with the process of surface modification of GaN by chlorine plasma. Then, the etching rate per cycle measured by in situ ellipsometry was 0.14 nm. Consequently, low-damage and precisely rate-controlled etching for GaN are promised.

DOI： 10.35848/1347-4065/ade9ce

Study on dry etching of epitaxially grown Si0.7Ge0.3 and Si using H2 diluted CF4 plasma 査読有り国際共著

Ozaki, K; Imai, Y; Tsutsumi, T; Imai, Y; Takada, N; Ishikawa, K; Yamamoto, Y; Wen, WC; Makihara, K

JAPANESE JOURNAL OF APPLIED PHYSICS 64 巻 ( 7 ) 2025年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers

The influence of H<inf>2</inf> dilution on CF<inf>4</inf>-plasma etching of Si<inf>0.7</inf>Ge<inf>0.3</inf> on Si(001) and Si on Si<inf>0.7</inf>Ge<inf>0.3</inf>/Si(001) was investigated. Selective etching of Si<inf>0.7</inf>Ge<inf>0.3</inf> with respect to Si was achieved without H<inf>2</inf> dilution, with the selectivity ratio of approximately 5.0. As the H<inf>2</inf> dilution ratio increased, the etch rate of Si<inf>0.7</inf>Ge<inf>0.3</inf> decreased monotonically, while that of Si remains nearly unchanged up to 5% H<inf>2</inf> dilution and the etch rate decreased by further H<inf>2</inf> dilution. With an increase in the H<inf>2</inf> dilution, fluorocarbon deposition on Si<inf>0.7</inf>Ge<inf>0.3</inf> and Si surface increased, resulting in suppression of surface roughening. Note that, the selectivity ratio of approximately 3.5 with keeping a surface flatness was achieved with 5% H<inf>2</inf> dilution. Furthermore, fluorocarbon passivation was more prominent on Si than Si<inf>0.7</inf>Ge<inf>0.3</inf>. We demonstrated lateral selective etching of Si<inf>0.7</inf>Ge<inf>0.3</inf> by etching of the 〈110〉-oriented sidewalls of Si<inf>0.7</inf>Ge<inf>0.3</inf>/Si/Si<inf>0.7</inf>Ge<inf>0.3</inf> stacked layers. These results are applicable to Si-nanosheet fabrication for gate-all-around field-effect transistors.

DOI： 10.35848/1347-4065/adea81

Selective dry etching of TiAlC over TiN using nonhalogen N2/H2 plasma 査読有り

Nguyen, TTN; Shinoda, K; Hsiao, SN; Maeda, K; Yokogawa, K; Izawa, M; Ishikawa, K; Hori, M

APPLIED SURFACE SCIENCE 691 巻頁： 162665 - 162665 2025年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Metal compounds such as TiAlC and TiN are used as work function metals in 3D multilayer logic semiconductor devices. Selective dry etching of these Ti compounds is highly desirable but challenging due to similar volatile products generated during the etching process. This study introduces the first instance of etch selectivity of TiAlC over TiN using low-pressure and low-temperature N<inf>2</inf>/H<inf>2</inf> plasma. A capacitively coupled plasma etcher generated N<inf>2</inf>/H<inf>2</inf> plasmas containing active species such as N, NH, and H to selectively modify TiAlC over TiN. The etching behavior and plasma-surface reaction were analyzed using in situ spectroscopic ellipsometry, optical emission spectroscopy, and X-ray photoelectron spectroscopy. Higher selectivity was achieved at higher substrate temperatures (up to 50 °C) or lower bias powers. The reaction between N<inf>2</inf>/H<inf>2</inf> plasma and TiAlC is more thermodynamically favorable than with TiN (ion-enhanced etching activation energy E<inf>a(TiAlC)</inf> = 0.044 eV/atom and E<inf>a(TiN)</inf> = 0.006 eV/atom). A process window for selective etching (TiAlC/TiN) was identified at lower bias powers, where chemical etching predominated. This study proposes a mechanism focusing on differences in chemical reactions between metal carbides and metal nitrides with N<inf>2</inf>/H<inf>2</inf> plasma to form different volatile products, highlighting the potential to develop nonhalogen chemistries for selective etching metal compounds.

DOI： 10.1016/j.apsusc.2025.162665

Low-temperature atomic layer etching of platinum via sequential wet-like reactions of plasma oxidation and complexation 査読有り

Nguyen, TTN; Akagi, D; Okato, T; Ishikawa, K; Hori, M

APPLIED SURFACE SCIENCE 687 巻頁： 162325 - 162325 2025年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Platinum (Pt) is a critical material in integrated circuits and microelectromechanical systems, yet it remains one of the most difficult-to-etch materials. High-temperature plasma etching can alter the original material properties or mix thin layers, thus limiting applications that require temperatures below 100 °C. Here, we present an atomic layer etching (ALE) method for Pt using sequential wet-like reactions involving high-density plasma oxidation and modified layer removal by formic acid (FA) vapor at temperatures below 80 °C. High-density oxygen radicals, generated from floating wire (FW)-assisted O<inf>2</inf>/Ar plasma referred to as wet-like O<inf>2</inf>/Ar plasma, act like a fluid of active O atoms dispersing in a medium of Ar atoms to fully oxidize the Pt surface and form a dominant oxidation state (Pt4+). The modified PtO<inf>2</inf> layer is then selectively removed from the underlayer Pt via neutralization and complexation reactions with FA vapor to form volatile organometallic compounds. This cyclic process, with minimal mechanical movement in the same process chamber, achieved etch depths of 0.3 to 0.7 nm per cycle at working pressures not exceeding 1000 Pa. The surface roughness of cyclically etched Pt film was controlled at the atomic level, maintaining a root mean square roughness of 0.7–0.9 nm, comparable to the initial film roughness. The mechanism for ALE with the formation of volatile Pt(IV) complexes is discussed.

DOI： 10.1016/j.apsusc.2025.162325

Effect of Low-temperature Plasma Irradiation on the Seedling Growth of Sugarcane and Erianthus 査読有り Open Access

松田大志, 寳川拓生, 杉浦史都, Ahyuni Destieka, Chanprame Sermsiri, Kaewkam Adisak, 仲田(狩野) 麻奈, 黒澤生吹, 石川健治, 井上健一, 江原宏

日本作物学会講演会要旨集 259 巻 ( 0 ) 頁： 46 - 46 2025年3月

Valence fragmentation dynamics of a promising low global warming etching gas CF3CHCF2 査読有り国際誌

Trung Nguyen Tran, Toshio Hayashi, Hiroshi Iwayama, and Kenji Ishikawa

SCIENTIFIC REPORTS 15 巻 ( 1 ) 頁： 9507 2025年3月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

C<inf>3</inf>HF<inf>5</inf> (CF<inf>3</inf>CHCF<inf>2</inf>, KSG14), a promising low global warming potential (GWP < 1) alternative to traditional perfluorocarbon etching gases for advanced integrated circuit manufacturing, particularly for high-aspect-ratio SiO<inf>2</inf>/SiN stacked layers in 3D flash memory. This study investigates the dissociative photoionization dynamics of C<inf>3</inf>HF<inf>5</inf> across 10.0–26.0 eV. Ion yield curves and breakdown diagrams reveal that C<inf>3</inf>HF<inf>5</inf> primarily fragments into C<inf>3</inf>HF<inf>5</inf>+, C<inf>3</inf>F<inf>5</inf>+, C<inf>3</inf>HF<inf>4</inf>+, C<inf>3</inf>F<inf>4</inf>+, C<inf>2</inf>F<inf>3</inf>+, and CF<inf>3</inf>+ ions. Appearance Energies of these fragments, determined from the ion yield curves, indicate fragmentation pathways at low electronic transitions. These findings underscore C<inf>3</inf>HF<inf>5</inf>’s potential as an environmentally friendly etching gas with excellent performance characteristics.

DOI： 10.1038/s41598-025-94119-6

Hydrofluoroethane plasma etching of SiN, SiO2, and poly-Si films with CHF2CF3, CF3CH3, and CHF2CH3 査読有り国際誌

Tran Trung Nguyen, Toshio Hayashi, Hiroshi Iwayama, Makoto Sekine, Masaru Hori, and Kenji Ishikawa

APPLIED SURFACE SCIENCE 684 巻頁： 161815 - 161815 2025年3月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Plasmas containing hydrofluorocarbon gases (CHF<inf>2</inf>CF<inf>3</inf>, CF<inf>3</inf>CH<inf>3</inf>, and CHF<inf>2</inf>CH<inf>3</inf>) are used for the selective removal of SiN, SiO<inf>2</inf>, and poly-Si films when manufacturing large-scale integrated circuits. Understanding the plasma chemistry of hydrofluorocarbons is important for gaining insight into the mechanisms of these selective-etching processes. The fragmental reactants produced by the reactive plasma are essential for evaluating and controlling highly accurate selective etching. This study examined such fragments using a primary dissociation ionization threshold quadrupole mass spectrometer at an electron energy of 20 eV. Their primary dissociative ionization thresholds were identified using photoelectron-photoion coincidence spectroscopy, with photon energies ranging from 10 to 28 eV. The results showed the following: (i) the CHF<inf>2</inf>CF<inf>3</inf> molecule dissociated into ions such as CHF<inf>2</inf>+ and C<inf>2</inf>HF<inf>4</inf>+, which formed secondary ions, such as CF<inf>3</inf>+ and CF<inf>2</inf>+. The F-rich reactants effectively enhanced the etching of both SiO<inf>2</inf> and SiN; (ii) the CF<inf>3</inf>CH<inf>3</inf> molecule dissociated into ions such as C<inf>2</inf>H<inf>2</inf>F+ and C<inf>2</inf>H<inf>2</inf>F<inf>2</inf>+, while the dominant CF<inf>3</inf>+ remained as a crucial fragment for the primary etching of SiO<inf>2</inf>; (iii) the CHF<inf>2</inf>CH<inf>3</inf> molecule predominantly yielded ions such as CHF<inf>2</inf>+, CF<inf>2</inf>CH<inf>3</inf>+ and C<inf>x</inf>H<inf>y</inf>+, promoting polymer film deposition on the surfaces of SiO<inf>2</inf> and poly-Si.

DOI： 10.1016/j.apsusc.2024.161815

Rate-controlled cycle etching of GaN by cycle exposure to BCl3 and F2-added Ar plasma at a substrate temperature of 400 °C 査読有り国際誌

Shohei Nakamura, Atsushi Tanide, Soichi Nadahara, Kenji Ishikawa, and Masaru Hori

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 43 巻 ( 2 ) 頁： 022202 2025年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B

Cycle etching of GaN with high etching rate controllability was achieved by cycle exposure to BCl<inf>3</inf> gas and F<inf>2</inf>-added Ar plasma at an ion energy of 23 eV and a substrate temperature of 400 °C. Surfaces chlorinated by exposure to BCl<inf>3</inf> gas were removed by ion bombardment during exposure to the F<inf>2</inf>-added Ar plasma. By controlling the plasma irradiation time, the etching amount per cycle for GaN can be regulated. Because of the lower energies of ion bombardments, no degradation of the cathodoluminescence intensity attributable to the energy bandgap edge of GaN was observed after cycle etching.

DOI： 10.1116/5.0239755

Nanoscale visualization of the anti-tumor effect of a plasma-activated Ringer's lactate solution 査読有り

Usuda, J; Yagyu, K; Tanaka, H; Hori, M; Ishikawa, K; Takahashi, Y

FARADAY DISCUSSIONS 257 巻 ( 0 ) 頁： 212 - 223 2025年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Faraday Discussions

Plasma-activated Ringer's lactate solutions (PALs), which are Ringer's lactate solutions treated with non-thermal atmospheric-pressure plasma, have an anti-tumor effect and can be used for chemotherapy. As the anti-tumor effect of the PAL is influenced by the cell-treatment time, it is necessary to monitor the structural changes of the cell surface with non-invasive, nanoscale, and time-lapse imaging to understand the anti-tumor effect. In this study, to characterize the anti-tumor effect of the PAL, we used scanning ion conductance microscopy (SICM), using glass nanopipettes as probes, to visualize the structural changes of the cell surface. SICM time-lapse topographic imaging visualized a decrease in the movement of lamellipodia in normal cells and cancer cells after the PAL treatment. Furthermore, in normal cells, protrusive structures were observed on the cell surface. Time-lapse imaging using SICM allowed us to characterize the differences in the morphological changes between the normal and cancer cells upon exposure to the PAL.

DOI： 10.1039/d4fd00116h

Developments in low-temperature plasma applications in Asia 査読有り国際共著国際誌

Attri, P; Ishikawa, K; Takeuchi, N; Nozaki, T; Rawat, RS; Chen, ZT; Bo, OY; Okumura, T; Fu, DN; Takahashi, K; Kim, DY; Chen, XZ; Kamataki, K; Takaki, K; Choi, EH; Hori, M; Koga, K; Shiratani, M

REVIEWS OF MODERN PLASMA PHYSICS 9 巻 ( 1 ) 頁： 6 2025年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Reviews of Modern Plasma Physics

Low-temperature plasmas, also known as non-thermal plasmas, are partially ionized gases whose electron temperatures are much higher than those of the ions and neutrals. Furthermore, gaseous molecules are partly dissociated, and the degree of dissociation is orders of magnitude larger than that calculated from the Boltzmann distribution at a given gas temperature. This distinguishing characteristic allows low-temperature plasma (LTP) to have diverse uses in many fields, including medical and biological, agriculture, environmental, and electronics and semiconductor applications. Applications of LTP have been increasing worldwide, but in this particular topic, we will focus on the advances in LTP applications in Asia.

DOI： 10.1007/s41614-025-00184-9

Achieving the In-plane Orientation of Carbon Nanowalls: Implications for Sensing, Energy Harvesting, and Nanobio Devices 査読有り

Iba, S; Kondo, H; Tsutsumi, T; Ishikawa, K; Hiramatsu, M; Hori, M

ACS APPLIED NANO MATERIALS 8 巻 ( 6 ) 頁： 2660 - 2668 2025年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Nano Materials

The in-plane orientation of the nanowalls was successfully realized through control of the ion energy and incidence angle during plasma-enhanced chemical vapor deposition processing of carbon nanowalls (CNWs). The ion energy and incidence angle were controlled by using a tilted stage, a metal mesh, and a radiofrequency (RF) stage bias. The degree of in-plane orientation was strongly dependent on the ion energy and incidence angle. The maximum degree of in-plane orientation was 0.65 for a stage tilt angle of 75° and an RF bias of 6 W. In the in-plane X-ray diffraction pattern, a graphite 002 peak was observed at a diffraction angle of 25.7° only when the X-rays were incident along the in-plane orientation direction of the CNWs. The electrical conductivity of the in-plane oriented CNWs was measured using the four-point probe method, and the in-plane conductivity was determined to be 2.5 times larger than that in the perpendicular direction. The conductivity was also improved by a factor of 2 compared to random CNWs. These results show that control of the degree of in-plane orientation leads to anisotropic electrical properties for vertically grown nanographene.

DOI： 10.1021/acsanm.4c01771

Plasma-enhanced atomic layer deposition of carbon films employing a cyclic process of N2/H2 plasma and α, α'-dichloro-p-xylene as a precursor 査読有り

Hu, LG; Tsutsumi, T; Kobayashi, N; Ishikawa, K; Hori, M

APPLIED SURFACE SCIENCE 681 巻頁： 161485 - 161485 2025年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

A novel concept and process were proposed for the plasma-enhanced atomic layer deposition (PE-ALD) of carbon films. α, α’-dichloro-p-xylene (DCX) was used to form the adsorption layer, which was modified using nitrogen/hydrogen (N<inf>2</inf>/H<inf>2</inf>) plasma. Through iterative molecular chemisorption and end-group substitution processes, the selective and precise control of carbon deposition by PE-ALD was achieved. The growth per cycle of this process was estimated to be 0.02–0.05 nm/cycle. To determine the chemical reactions that occurred during the PE-ALD process, the IR spectra observed using in-situ Fourier transform infrared spectroscopy were analyzed. The decrease in the Si-OH bond at 3740 cm−1 and the saturation of the increase in CH bending at 1250 cm−1 revealed that the deposition of a DCX monolayer via a dehydrochlorination reaction with isolated OH bonding on SiO<inf>2</inf> has been successfully achieved. The change in N(−H)<inf>x</inf> stretching during the N<inf>2</inf>/H<inf>2</inf> plasma treatment indicated the substitution of exposed C-Cl bonding with C-NH<inf>2</inf> bonding on the chemisorbed DCX monolayer surface. Additionally, the composition of the carbon films after 200-cycle PE-ALD was analyzed. Finally, the realization of the concept for PE-ALD of carbon film was confirmed by surface analysis.

DOI： 10.1016/j.apsusc.2024.161485

Analysis of the synergetic effect of process parameters of hydrogenated amorphous carbon deposition in plasma-enhanced chemical vapor deposition using machine learning 査読有り

Ando, Y; Kondo, H; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

DIAMOND AND RELATED MATERIALS 151 巻頁： 111687 - 111687 2025年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Diamond and Related Materials

The synergetic effects of process parameters on hydrogenated amorphous carbon (a-C:H) films properties were quantitatively analyzed in plasma-enhanced chemical vapor deposition. Predictive models, created from experimental datasets and machine learning, indicate a synergetic effect between the H<inf>2</inf> ratio and ion energy impacting on the substrate. At a H<inf>2</inf> ratio of 75 %, etch rates of 200 nm/min were predicted, regardless of radio frequency (RF) bias. These rates decreased to 120–140 nm/min at lower H<inf>2</inf> ratios, primarily depending on RF bias. Quadrupole mass spectrometry and Raman scattering were used to investigate the underlying mechanisms. High H<inf>2</inf> ratios led to a greater presence of low-mass hydrogen-rich molecules in the plasma. The C<inf>2</inf>H<inf>3</inf> radical intensity at a 75 % H<inf>2</inf> ratio was 15 times greater than that at 0 % at an RF bias of 50 W, and similar trends were observed for other low-mass neutrals. The synergetic effects of H<inf>2</inf> ratio and RF bias decreased the film's hydrogen content. Machine learning and those diagnostics revealed that ion bombardment induces dehydrogenation of a-C:H, influenced by hydrogen-rich species. This study demonstrates that machine learning can uncover complex plasma processes and optimize material synthesis.

DOI： 10.1016/j.diamond.2024.111687

Pseudo-Wet Plasma Mechanism Enabling High-Throughput Dry Etching of SiO2 by Cryogenic-Assisted Surface Reactions 査読有り

Epitaxial growth of high-quality GaN with a high growth rate at low temperatures by radical-enhanced metalorganic chemical vapor deposition (vol 14, 10861, 2024) 査読有り国際誌 Open Access

Dhasiyan, AK; Amalraj, FW; Jayaprasad, S; Shimizu, N; Oda, O; Ishikawa, K; Hori, M

SCIENTIFIC REPORTS 14 巻 ( 1 ) 頁： 30575 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Correction to: Scientific Reportshttps://doi.org/10.1038/s41598-024-61501-9, published online 13 May 2024 The original version of this Article contained an error in the legend of Figures 20 and 21, where an inset was mistakenly included. Figure 20 “GaN on a GaN template under the best conditions with a growth time of 15 min. (a) Surface morphology (inset is the RHEED pattern), (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” now reads, “GaN on a GaN template under the best conditions with a growth time of 15 min. (a) Surface morphology, (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” And Figure 21 “GaN on a bulk GaN substrate under the best conditions with a growth time of 15 min. (a) Surface morphology (inset is the RHEED pattern), (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” now reads, “GaN on a bulk GaN substrate under the best conditions with a growth time of 15 min. (a) Surface morphology, (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” The original Article has been corrected.

DOI： 10.1038/s41598-024-82619-w

Hsiao, SN; Sekine, M; Britun, N; Mo, MKT; Imai, Y; Tsutsumi, T; Ishikawa, K; Iijima, Y; Suda, R; Yokoi, M; Kihara, Y; Hori, M

SMALL METHODS 8 巻 ( 12 ) 頁： e2400090 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Small Methods

Manufacturing semiconductor devices requires advanced patterning technologies, including reactive ion etching (RIE) based on the synergistic interactions between ions and etch gas. However, these interactions weaken as devices continuously scale down to sub-nanoscale, primarily attributed to the diminished transport of radicals and ions into the small features. This leads to a significant decrease in etch rate (ER). Here, a novel synergistic interaction involving ions, surface-adsorbed chemistries, and materials at cryogenic temperatures is found to exhibit a significant increase in the ER of SiO<inf>2</inf> using CF<inf>4</inf>/H<inf>2</inf> plasmas. The ER increases twofold when plasma with H<inf>2</inf>/(CF<inf>4</inf> + H<inf>2</inf>) = 33% is used and the substrate temperature is lowered from 20 to −60 °C. The adsorption of HF and H<inf>2</inf>O on the SiO<inf>2</inf> surface at cryogenic temperatures is confirmed using in situ Fourier transform infrared spectroscopy. The synergistic interactions of the surface-adsorbed HF/H<inf>2</inf>O as etching catalysts and plasma species result in the ER enhancement. Therefore, a mechanism called “pseudo-wet plasma etching” is proposed to explain the cryogenic etching process. This synergy demonstrates that the enhanced etch process is determined by the surface interactions between ions, surface-adsorbed chemistry, and the material being etched, rather than interactions between ion and gas phase, as observed in the conventional RIE.

DOI： 10.1002/smtd.202400090

Low-temperature plasma as a strategy to achieve SDGs 査読有り

Tanaka, H; Ishikawa, K; Toyokuni, S

FREE RADICAL RESEARCH 58 巻 ( 10 ) 頁： 594 - 595 2024年10月

Selective removal of single-layer graphene over double-layer graphene on SiO2 by remote oxygen plasma irradiation 査読有り

Hu, LG; Ishikawa, K; Nguyen, TTN; Hsiao, SN; Hori, M

APPLIED SURFACE SCIENCE 669 巻頁： 160598 - 160598 2024年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Graphene sheet transferred onto the SiO<inf>2</inf> substrate has various types at different regions such as single-layer graphene (SLG), double-layer graphene (DLG), and multi-layer graphene (MLG). These layers were identified by Raman analysis of 2D band position around 2700 cm−1 and full width at half maximum (FWHM). The transferred graphene sheets on SiO<inf>2</inf> were remotely irradiated by oxygen plasma without energetic ions at a room temperature. At the beginning of the oxygen plasma irradiation, the carbons on the surface of the graphene sheets were oxidized and the 2D-FWHMs were broadened due to an increase of defects on the basal plane. By controlling the plasma irradiation time up to 120 min, selectively stripping away the SLG regions on the SiO<inf>2</inf> surface was observed while leaving the other DLG and MLG regions. The difference in attractive forces resulted in favorable desorption of carbon atoms occurred in the oxidized SLG regions on SiO<inf>2</inf> surface by the remote oxygen plasma irradiation.

DOI： 10.1016/j.apsusc.2024.160598

High-Speed Removal Process for Organic Polymers by Non-Thermal Atmospheric-Pressure Spark Discharge at Room Temperature and Its Mechanism 査読有り

Sakamoto, Y; Tsutsumi, T; Tanaka, H; Ishikawa, K; Hashizume, H; Hori, M

COATINGS 14 巻 ( 10 ) 頁： 1339 - 1339 2024年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Coatings

Heel marks (HMs) are a type of dirt stain consisting of polyester-based urethane rubber on polyvinyl chloride (PVC) floor surfaces. The rapid removal of HMs was achieved by using non-thermal atmospheric-pressure plasma technology. Mimetic HMs were prepared by coating PVC floor samples with HMs to a thickness of 13.9 μm. The removal area, thickness, and volume were measured after applying spark discharges at high voltage and a repetition rate of 50 kHz. The treated surfaces were analyzed by using X-ray photoelectron spectroscopy (XPS) and pyrolysis–gas chromatography with time-of-flight mass spectrometry (Py-GC/TOFMS). Removal rates of 20 mm2/min in area, 52 mm3/min in volume, and 7 μm/min in depth were achieved with an inter-electrode distance of 10.0 mm and an air flow rate of 20 standard liters per minute. A removal depth of 10 μm/min was achieved without air supply. The mechanism of stain removal by spark discharge was modeled by decomposing the original high-molecular-weight molecules in polyester-based urethane rubber into low-molecular-weight molecules, such as methylene diisocyanate (MDI) components. The results of this study may facilitate the development of a novel electric vacuum cleaner capable of removing floor stains.

DOI： 10.3390/coatings14101339

Nonhalogen Dry Etching of Metal Carbide TiAlC by Low-Pressure N2/H2 Plasma at Room Temperature 査読有り

Nguyen, TTN; Shinoda, K; Hsiao, SN; Maeda, K; Yokogawa, K; Izawa, M; Ishikawa, K; Hori, M

ACS APPLIED MATERIALS & INTERFACES 16 巻 ( 39 ) 頁： 53195 - 53206 2024年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Materials and Interfaces

Ternary metal carbide TiAlC has been proposed as a metal gate material in logic semiconductor devices. It is a hard-to-etch material due to the low volatility of the etch byproducts. Here, a simple, highly controllable, and dry etching method for TiAlC has been first presented using nonhalogen N<inf>2</inf>/H<inf>2</inf> plasmas at low pressure (several Pa) and 20 °C. A capacitively coupled plasma etcher was used to generate N<inf>2</inf>/H<inf>2</inf> plasmas containing active species, such as N, NH, and H to modify the metal carbide surface. The etch rate of TiAlC was obtained at 3 nm/min by using the N<inf>2</inf>/H<inf>2</inf> plasma, whereas no etching occurred with pure N<inf>2</inf> plasma or pure H<inf>2</inf> plasma under the same conditions. The surface roughness of the TiAlC film etched by N<inf>2</inf>/H<inf>2</inf> plasma was controlled at the atomic level. A smooth etched surface was achieved with a root-mean-square roughness of 0.40 nm, comparable to the initial roughness of 0.44 nm. The plasma properties of the N<inf>2</inf>/H<inf>2</inf> plasmas were diagnosed by using a high-resolution optical emission spectrometer, detecting the NH molecular line at 336 nm. The etching behavior and plasma-surface reaction between N<inf>2</inf>/H<inf>2</inf> plasma and TiAlC were investigated by using in situ spectroscopic ellipsometry, in situ attenuated total reflectance-Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy. The findings indicate that the N-H, C-N, and Ti(Al)-N bonds form on the TiAlC surface etched by the N<inf>2</inf>/H<inf>2</inf> plasmas. The mechanism for etching of TiAlC involving transformation reactions between inorganic materials (metal carbides) and inorganic etchants (N<inf>2</inf>/H<inf>2</inf> plasma) to form volatile organic compounds such as methylated, methyl-aminated, and aminated metals is proposed. Nonhalogen or nonorganic compound etchants were used during the etching process. The study provides useful insights into microfabrication for large-scale integrated circuits.

DOI： 10.1021/acsami.4c11025

Dry Process 2023 査読有り

Koga K., Takeda K., Toyoda H., Ishikawa K., Ichiki T., Nunomura S., Kurihara K., Kuboi N., Ohta T., Takenaka K.

Japanese Journal of Applied Physics Part 1 Regular Papers and Short Notes and Review Papers 63 巻 ( 8 ) 2024年8月

Effects of Plasma Ions/Radicals on Kinetic Interactions in Nanowall Deposition: A Review 査読有り

Ishikawa, K

ADVANCED ENGINEERING MATERIALS 26 巻 ( 16 ) 頁： 2400679 2024年8月

担当区分：筆頭著者,　最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advanced Engineering Materials

Recent advances in the growth of carbon nanowalls (CNWs) and vertical graphene nanosheets using various plasma-enhanced chemical vapor deposition (PECVD) methods are reviewed in this article. Growth methods are classified into hot- and cold-wall reactors equipped with diverse plasma generation systems, and their respective characteristics are summarized, with particular attention to the behavior of reactive species, such as ions and radicals, generated within the plasma. Recent progress in this research domain is outlined for each method, and an organized account of the chemical kinetic phenomena occurring within the plasma is provided. Finally, future perspectives are discussed. Fundamental data are obtained through real-time in situ measurements of ions and radicals, and the construction of a database from these data offers microscopic insights that significantly enhance processing outcomes for macroscopically controlling the mechanical shapes and chemical properties of CNWs.

DOI： 10.1002/adem.202400679

Future of plasma etching for microelectronics: Challenges and opportunities 査読有り国際共著

Oehrlein, GS; Brandstadter, SM; Bruce, RL; Chang, JP; Demott, JC; Donnelly, VM; Dussart, R; Fischer, A; Gottscho, RA; Hamaguchi, S; Honda, M; Hori, M; Ishikawa, K; Jaloviar, SG; Kanarik, KJ; Karahashi, K; Ko, AKTR; Kothari, H; Kuboi, N; Kushner, MJ; Lill, T; Luan, PS; Mesbah, A; Miller, E; Nath, S; Ohya, Y; Omura, M; Park, C; Poulose, J; Rauf, S; Sekine, M; Smith, TG; Stafford, N; Standaert, T; Ventzek, PLG

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 42 巻 ( 4 ) 頁： 041501 2024年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B

Plasma etching is an essential semiconductor manufacturing technology required to enable the current microelectronics industry. Along with lithographic patterning, thin-film formation methods, and others, plasma etching has dynamically evolved to meet the exponentially growing demands of the microelectronics industry that enables modern society. At this time, plasma etching faces a period of unprecedented changes owing to numerous factors, including aggressive transition to three-dimensional (3D) device architectures, process precision approaching atomic-scale critical dimensions, introduction of new materials, fundamental silicon device limits, and parallel evolution of post-CMOS approaches. The vast growth of the microelectronics industry has emphasized its role in addressing major societal challenges, including questions on the sustainability of the associated energy use, semiconductor manufacturing related emissions of greenhouse gases, and others. The goal of this article is to help both define the challenges for plasma etching and point out effective plasma etching technology options that may play essential roles in defining microelectronics manufacturing in the future. The challenges are accompanied by significant new opportunities, including integrating experiments with various computational approaches such as machine learning/artificial intelligence and progress in computational approaches, including the realization of digital twins of physical etch chambers through hybrid/coupled models. These prospects can enable innovative solutions to problems that were not available during the past 50 years of plasma etch development in the microelectronics industry. To elaborate on these perspectives, the present article brings together the views of various experts on the different topics that will shape plasma etching for microelectronics manufacturing of the future.

DOI： 10.1116/6.0003579

Low-temperature growth at 225 °C and characterization of carbon nanowalls synthesized by radical injection plasma-enhanced chemical vapor deposition 査読有り Open Access

Minh, NQ; Van Nong, N; Oda, O; Ishikawa, K; Hori, M

VACUUM 224 巻頁： 113180 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Vacuum

The synthesis of carbon nanowalls (CNWs) necessitated a substrate heating temperature above 600 °C. This study describes a low-temperature growth at 225 °C and characterization of CNWs synthesized by the radical injection plasma-enhanced chemical vapor deposition. To investigate the effect of temperature on the growth process, CNWs were synthesized at various temperatures ranging from 200 °C to 700 °C. The morphology of the CNWs observed with a scanning electron microscope shows that wall density increases as substrate temperature decreases. The Raman spectroscopy analysis indicates that CNWs grown at 225 °C have higher defect levels than those grown at higher temperatures, such as 700 °C. Transmission electron microscopy confirmed the presence of multiple graphene layers in the CNWs grown at 225 °C. The water contact angle results revealed that CNWs grown at 225 °C had higher hydrophobicity than those grown at higher temperatures, opening up the potential for CNW applications.

DOI： 10.1016/j.vacuum.2024.113180

Epitaxial growth of high-quality GaN with a high growth rate at low temperatures by radical-enhanced metalorganic chemical vapor deposition 査読有り

Dhasiyan, AK; Amalraj, FW; Jayaprasad, S; Shimizu, N; Oda, O; Ishikawa, K; Hori, M

SCIENTIFIC REPORTS 14 巻 ( 1 ) 頁： 10861 2024年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Using our recently developed radical-enhanced metalorganic chemical vapor deposition (REMOCVD) technique, we have grown gallium nitride (GaN) on bulk GaN and GaN on Si templates. Three features make up this system: (1) applying very high-frequency power (60 MHz) to increase the plasma density; (2) introducing H<inf>2</inf> and N<inf>2</inf> gas in the plasma discharge region to produce active NH<inf>x</inf> radical species in addition to nitrogen radicals; and (3) supplying radicals under remote plasma arrangement with a Faraday cage to suppress charged ions and photons. Using this new REMOCVD system, it was found that high-quality crystals can be grown at lower temperatures than that of MOCVD but the disadvantage was that the growth rate was smaller as 0.2–0.8 μm/h than that by MOCVD. In the present work, we have used a pBN inner shield to prevent the deactivation of radicals to increase the growth rate. The growth conditions such as the plasma power, trimethylgallium (TMG) source flow rate, N<inf>2</inf> + H<inf>2</inf> gas mixture flow rate, and the ratio of N<inf>2</inf>/H<inf>2</inf> were optimized and it was found that the growth rate could be increased up to 3.4 μm/h with remarkably high crystalline quality comparable to that of MOCVD. The XRD-FWHM of GaN grown on the GaN/Si template and the bulk GaN substrate were 977 arcsec and 72 arcsec respectively. This work may be very promising to achieve high-power GaN/GaN devices.

DOI： 10.1038/s41598-024-61501-9

In situ atom-resolved observation of Si (111) 7x7 surface with F radical and Ar ion irradiation simulated atomic layer etching 査読有り

Tsutsumi, T; Asano, A; Kondo, H; Ishikawa, K; Sekine, M; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 42 巻 ( 3 ) 頁： 032603 2024年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology A Vacuum Surfaces and Films

Ar ions with controlled energy and doses, along with radicals in CF<inf>4</inf> plasma, were irradiated separately onto a Si (111) 7 × 7 surface by using a plasma beam reactor. The crystal structure and the chemical bonds on the surface were analyzed by scanning tunneling microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy without air exposure of the samples. The SiF layer formed by F radical irradiation was completely removed by a desorption reaction induced by heating at 600 °C, resulting in an atomically flat surface that maintained the crystal structure. The 7 × 7 structure, which was reconstructed by each irradiation process alone, was not reconstructed because of the synergistic effects of F radicals and Ar ions in the cyclic CF<inf>4</inf>/Ar plasma used to simulate an atomic layer etching process. The cyclic CF<inf>4</inf>/Ar plasma process inhibited the reconstruction of the crystal structure by forming a mixture region that included Si, F, and C atoms.

DOI： 10.1116/6.0003432

Nitrogen admixture effects on growth characteristics and properties of carbon nanowalls 査読有り Open Access

Christy, PRD; Van Nong, N; Britun, N; Minh, NQ; Nguyen, TTN; Kondo, H; Oda, O; Ishikawa, K; Hori, M

THIN SOLID FILMS 795 巻頁： 140322 2024年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Thin Solid Films

The plasma functionalization of carbon nanowalls (CNWs) is of great interest due to their potential applications in electron field emission and energy storage devices. In this study, the effects of nitrogen on the growth and properties of CNWs are thoroughly investigated by varying a wide range of the N<inf>2</inf> concentrations in the CH<inf>4</inf>/H<inf>2</inf>/N<inf>2</inf> discharge plasma. Nitrogen-doped carbon nanowalls (N–CNWs) were synthesized in a single-step growth using the hydrogen radical injection plasma-enhanced chemical vapor deposition technique. The formation of dense N–CNWs was found to be enhanced by nitrogen and was three times higher in the sample with a 150 sccm N<inf>2</inf> flow rate than in the sample without N<inf>2</inf> addition (N-0). As the N<inf>2</inf> concentration increased from 0 to 200 sccm, the morphology of CNWs changed from relatively straight to curly-like nanowall structures. A high-resolution optical emission spectroscopic observation shows that as N<inf>2</inf> flow increased, CN radicals became the dominant species, suppressing the formation of C<inf>2</inf> and CH. Photoelectron spectroscopy analysis revealed the nitrogen doping effect on graphene layers at high N<inf>2</inf> concentrations. According to Raman and Transmission Electron Microscopy analyses, the N–CNWs had more branched and thicker nanowalls with higher defect concentrations than the N-0 sample. The wettability of N–CNWs was improved, particularly for the sample with a N<inf>2</inf> flow rate of 150 sccm.

DOI： 10.1016/j.tsf.2024.140322

Dissociative properties of C4F6 obtained using computational chemistry 査読有り

Hayashi, T; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 63 巻 ( 4 ) 頁： 04SP26 2024年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The electronic properties of C<inf>4</inf>F<inf>6</inf> were investigated by using computational chemistry to clarify the dissociative channels in the process plasma. The results show the mainly ionized ion is C<inf>3</inf>F<inf>3</inf>+ (CF<inf>2</inf>=C=CF+; propargyl ion) which is observed in the mass spectrum with the electron energy of 70 eV, and the intermediate molecular structure to produce C<inf>3</inf>F<inf>3</inf>+ ion is methyl allene ion (CF<inf>2</inf>=C=CF-CF<inf>3</inf>+). The molecular ion C<inf>4</inf>F<inf>6</inf>+ is also mainly produced in the ionization threshold region. For the excited states, the calculated results suggest that CF<inf>2</inf>CFCF + CF<inf>2</inf> dissociation takes place in the energy region higher than 7.0 eV and C<inf>2</inf>F<inf>3</inf> + C<inf>2</inf>F<inf>3</inf> dissociation takes place in the energy region higher than 8.0 eV. In the electron attachment process, the vertical electron attachment energy was calculated as 1.1 eV and the nonadiabatic negative ion energy was −0.2 eV lower than the energy of neutral C<inf>4</inf>F<inf>6</inf>

DOI： 10.35848/1347-4065/ad3166

Elaborate cooperation of poly(rC)-binding proteins 1/2 and glutathione in ferroptosis induced by plasma-activated Ringer's lactate 査読有り

Inhibition of glutamine metabolism increases sensitivity to plasma-activated medium-induced cytotoxicity 査読有り

Tanaka, S; Hayashi, S; Otsuka, T; Kamiya, T; Ishikawa, K; Hara, H

FREE RADICAL RESEARCH 58 巻 ( 3 ) 頁： 170 - 179 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Free Radical Research

Non-thermal atmospheric pressure plasma (NTP), an ionized gas containing electrons, ions, radicals, and photons, has various biological effects, including wound healing and anticancer effects. Plasma-activated medium (PAM), which is prepared by irradiating medium with NTP, preferentially kills cancer cells. Large amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS) included in PAM are closely related to its anticancer effects. The precise mechanism of PAM-induced cytotoxicity is not fully understood; however, PAM exposure has been reported to reduce cellular energy metabolism. Glutamine (Gln) is an important amino acid as an energy source in cancer cells. Gln is converted to glutamate by glutaminase (GLS), and is utilized to synthesize ATP and glutathione (GSH). Expression levels of GLS have been shown to be higher in certain types of cancers. In this study, we examined the effects of GLS inhibition on PAM cytotoxicity using breast cancer MDA-MB-231 cells. Pretreatment with BPTES, a glutaminase 1 (GLS1) inhibitor, dose-dependently enhanced PAM-induced cell death. PAM-induced ROS production and γ-H2AX formation, a DNA damage marker, were increased in cells pretreated with BPTES compared with PAM alone. BPTES pretreatment enhanced a PAM-induced decrease in intracellular GSH, indicating the possibility that BPTES reduces the antioxidant capacity of MDA-MB-231 cells. In addition, BPTES pretreatment enhanced PAM-induced loss of the mitochondrial membrane potential and reduction of ATP production. Moreover, GLS1 knockdown promoted PAM-induced cell death. Taken together, the combination of GLS1 inhibitors such as BPTES is considered to be useful for enhancing the cytotoxic effects of PAM against cancer cells.

DOI： 10.1080/10715762.2024.2332343

Plasma-Driven Sciences: Exploring Complex Interactions at Plasma Boundaries 査読有り Open Access

Ishikawa, K; Koga, K; Ohno, N

PLASMA 7 巻 ( 1 ) 頁： 160 - 177 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma

Plasma-driven science is defined as the artificial control of physical plasma-driven phenomena based on complex interactions between nonequilibrium open systems. Recently, peculiar phenomena related to physical plasma have been discovered in plasma boundary regions, either naturally or artificially. Because laboratory plasma can be produced under nominal conditions around atmospheric pressure and room temperature, phenomena related to the interaction of plasma with liquid solutions and living organisms at the plasma boundaries are emerging. Currently, the relationships between these complex interactions should be solved using science-based data-driven approaches; these approaches require a reliable and comprehensive database of dynamic changes in the chemical networks of elementary reactions. Consequently, the elucidation of the mechanisms governing plasma-driven phenomena and the discovery of the latent actions behind these plasma-driven phenomena will be realized through plasma-driven science.

DOI： 10.3390/plasma7010011

Jiang, L; Zheng, H; Ishida, M; Lyu, Q; Akatsuka, S; Motooka, Y; Sato, K; Sekido, Y; Nakamura, K; Tanaka, H; Ishikawa, K; Kajiyama, H; Mizuno, M; Hori, M; Toyokuni, S

FREE RADICAL BIOLOGY AND MEDICINE 214 巻頁： 28 - 41 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Free Radical Biology and Medicine

Reactive species are involved in various aspects of neoplastic diseases, including carcinogenesis, cancer-specific metabolism and therapeutics. Non-thermal plasma (NTP) can directly provide reactive species, by integrating atmospheric and interjacent molecules as substrates, to represent a handy strategy to load oxidative stress in situ. NTP causes apoptosis and/or ferroptosis specifically in cancer cells of various types. Plasma-activated Ringer's lactate (PAL) is another modality at the preclinical stage as cancer therapeutics, based on more stable reactive species. PAL specifically kills malignant mesothelioma (MM) cells, employing lysosomal ·NO as a switch from autophagy to ferroptosis. However, the entire molecular mechanisms have not been elucidated yet. Here we studied cytosolic iron regulations in MM and other cancer cells in response to PAL exposure. We discovered that cells with higher catalytic Fe(II) are more susceptible to PAL-induced ferroptosis. PAL caused a cytosolic catalytic Fe(II)-associated pathology through iron chaperones, poly (rC)-binding proteins (PCBP)1/2, inducing a disturbance in glutathione-regulated iron homeostasis. PCBP1/NCOA4-mediated ferritinophagy started at a later phase, further increasing cytosolic catalytic Fe(II), ending in ferroptosis. In contrast, PCBP2 after PAL exposure contributed to iron loading to mitochondria, leading to mitochondrial dysfunction. Therapeutic effect of PAL was successfully applied to an orthotopic MM xenograft model in mice. In conclusion, PAL can selectively sensitize MM cells to ferroptosis by remodeling cytoplasmic iron homeostasis, where glutathione and PCBPs play distinct roles, resulting in lethal ferritinophagy and mitochondrial dysfunction. Our findings indicate the clinical application of PAL as a ferroptosis-inducer and the potential of PCBPs as novel targets in cancer therapeutics.

DOI： 10.1016/j.freeradbiomed.2024.02.001

液中プラズマによるナノグラフェンの高速合成と機能化 Open Access

石川健治, 堤隆義, 近藤博基, 堀勝, 平松美根男

表面と真空 67 巻 ( 2 ) 頁： 77 - 82 2024年2月

Surface sulfurization of amorphous carbon films in the chemistry of oxygen plasma added with SO2 or OCS for high-aspect-ratio etching 査読有り

Ishikawa, K; Nguyen, TTN; Aoki, Y; Sato, H; Kawakami, J; Tsuno, S; Hsiao, SN; Hori, M

APPLIED SURFACE SCIENCE 645 巻頁： 158876 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Etching of oxygen-based plasmas with sulfur dioxide (SO<inf>2</inf>) or carbonyl sulfide (OCS) can form high-aspect-ratio (HAR) features of amorphous carbon films as carbon hard masks (CHM). The etched profiles showing shapes such as bowing or tapering are essentially dependent on the partial pressures of SO<inf>2</inf> or OCS in the O<inf>2</inf> plasma. The surface treated after the OCS-added plasma exhibited strong sulfurization by S<inf>2</inf> and CS species in S 2p of the X-ray photoelectron spectroscopy (XPS). The gas-phase interactions in the sulfur-oxygen-carbon system generated atoms and molecules, such as O, O+, and O<inf>2</inf>+, which etched at the bottom and, conversely, SO, CO, CS, CS<inf>2</inf>, and S<inf>2</inf>, which inhibited isotropic etching at the sidewalls of the HAR features. The chemical reactions of the CS sulfurizing precursors in the gas phase were monitored by comparing their optical emission intensities at a wavelength of 257 nm with those of SO<inf>2</inf> at approximately 320 nm. The optimization of the HAR profiles of the CHM can be controlled by sidewall sulfurization of the CHM to obtain desirable profile shapes for the HAR features.

DOI： 10.1016/j.apsusc.2023.158876

Oxygen radical irradiation transforms an organic fertilizer L-tryptophan into an environment and human-friendly bactericide 査読有り

Iwata, N; Ishikawa, K; Nishikawa, Y; Kato, H; Shimizu, M; Kato, M; Tanaka, H; Ito, M; Hori, M

ENVIRONMENTAL TECHNOLOGY & INNOVATION 33 巻頁： 103496 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Environmental Technology and Innovation

Organic fertilizers are useful in hydroponic agriculture to bring about a sustainable society with minimal pollution. Irradiation of L-tryptophan (L-Trp) solutions with electrically neutral atomic oxygen produces immediate bactericidal activity. After oxygen radical irradiation of an L-Trp-containing Escherichia coli suspension at pH 6.3 for 5 min, a colony-forming unit assay showed a 6-log reduction in the number of surviving E. coli. Kynurenine and N’-formylkynurenine were identified as irradiation products in the solution using liquid chromatography–mass spectroscopy and nuclear magnetic resonance spectroscopy. Tryptophan radicals (Trp•) are precursors of kynurenine and N’-formylkynurenine and are detected using spin-trap electron spin resonance. The bactericidal effect is mediated by central carbon metabolism via enzyme deactivation in E. coli. Enzymatic deactivation via the oxygen radical irradiation of a solution containing the amino acid L-Trp eventually resulted in bacterial death.

DOI： 10.1016/j.eti.2023.103496

High linear energy transfer (LET) nature of alanine radical yield by soft X-ray irradiations studied by electron spin resonance (ESR) applications 査読有り

Nakagawa, S; Yokoya, A; Ohara, M; Usami, N; Asada, M; Fujiwara, M; Nakamura, T; Ishikawa, K

RADIATION PHYSICS AND CHEMISTRY 214 巻頁： 111304 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Radiation Physics and Chemistry

Radicals produced in alanine by irradiation of 2–7 keV X-rays were investigated by ESR applications; i.e., CW-ESR, pulse-ESR and ESR imaging. The relative radical yield decreased with the decreasing photon energy and the increasing dose. The 2D imaging showed that the radical concentration at the surface was extremely low even though the absorption of X-rays exponentially decreased with the penetration depth. The depth of the radical concentration peak was almost the same as the penetration depth for the X-ray irradiation with an energy lower than 5-keV. The product formed by radical recombination was observed by an LC/MS (liquid chromatograph-mass spectrum) analysis. For the soft X-ray irradiation, many radicals will be lost by the efficient radical-radical recombination due to the higher density of the radicals, similar to the high-LET irradiation by heavy ions. The spin-spin relaxation rate (1/T<inf>2</inf>), which correlates with the radical concentration, increased by the decreasing photon energy. The values of 1/T<inf>2</inf> for the soft X-rays were compatible to that for the heavy ions with the high-LET. Based on these observations, it is concluded that the effects of irradiation by soft X-rays are similar to high-LET irradiation.

DOI： 10.1016/j.radphyschem.2023.111304

Science and Applications of Plasma-Activated Solutions: Current Trends and Future Directions 査読有り国際共著

Tanaka H., Mizuno M., Ishikawa K., Miron C., Okazaki Y., Toyokuni S., Nakamura K., Kajiyama H., Ito M., Hori M.

Plasma Medicine 14 巻 ( 1 ) 頁： 67 - 76 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Medicine

Recent research into plasma-activated solutions has unveiled their considerable potential across a range of applications, including cancer treatment, industrial processes, and environmental management. This review summarizes key findings from recent studies on the effects of plasma-activated solutions, focusing on their ability to induce cell death in glioblastoma cells, enhance ethanol production in yeast, and convert organic compounds into environmentally friendly substances. The review highlights the mechanisms by which plasma-activated solutions exert their effects, such as oxidative stress induction and cellular metabolic alterations. Addition-ally, it discusses the implications of these findings for overcoming challenges in cancer therapy, improving agricultural practices, and developing novel environmental technologies. The ongoing advancements in plasma technology offer promising avenues for future research and applications, underscoring its transformative potential in both scientific and practical domains.

DOI： 10.1615/PlasmaMed.v14.i1.50

Cold Atmospheric Pressure Plasma-Activated Liquids for Cancer Treatment 査読有り

Miron, C; Hiromasa, T; Britun, N; Hashizume, H; Ishikawa, K; Du, LY; Yamakawa, T; Kurebayashi, Y; Kondo, T; Kondo, H; Kajiyama, H; Toyokuni, S; Mizuno, M; Hori, M

ADVANCES IN DIGITAL HEALTH AND MEDICAL BIOENGINEERING, VOL 3, EHB-2023 111 巻頁： 150 - 162 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ifmbe Proceedings

Low-temperature plasma (LTP) is a promising tool that can assist in cancer treatment. Plasma-treated liquids have shown a selective cytotoxic effect on cancer cells attributed to reactive species formed in discharge, but this mechanism is not completely understood. In this study, the chemical compounds formed by plasma irradiation of Ringer’s lactate solutions and their effects on non-tumorigenic breast epithelial cells (MCF-10A) and breast cancer cells (MCF-7) were investigated. Among these compounds, glyceric acid increased the cell viability by more than two-fold compared to the control samples for MCF-10A and MCF-7 cells, whereas the tricarballylic acid had a pronounced cytotoxic effect on the cells when incubated with solutions of 0.6 mM to 50 mM concentrations. A good selectivity in killing the cancer cells was observed when the chemical compounds identified in plasma-treated liquids (such as ethyl acetate, glyceric acid, and tricarballylic acid) were used in a mixture solution of a certain concentration. The results show that the LTP-generated chemical compounds have both, stimulatory and inhibitory effects on cell viability, and the best selectivity is achieved only when these compounds are combined in a certain amount and have a synergistic effect, completely killing only the cancer cells.

DOI： 10.1007/978-3-031-62523-7_17

Bias-supply timing tailored to the aspect ratio dependence of silicon trench etching in Ar plasma with alternately injected C4F8 and SF6 査読有り Open Access

Yoshie, T; Ishikawa, K; Nguyen, TTN; Hsiao, SN; Tsutsumi, T; Sekine, M; Hori, M

APPLIED SURFACE SCIENCE 638 巻頁： 157981 2023年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

In semiconductor device fabrication, the feature profiles of a high-aspect-ratio (HAR) Si trench is needed to be controlled considering aspect-ratio-dependent etching (ARDE). This is achieved by a cyclic process in which Ar plasma is sustained while C<inf>4</inf>F<inf>8</inf> and SF<inf>6</inf> are alternately injected and a short-period supply of a substrate bias is provided. Presently, the transient behaviors of gaseous and surface reactions are dynamically revealed by measuring the plasma parameters using a surface wave probe and optical emission spectroscopy. When the etched surface is fluorinated during the cycle, an ARDE-free Si-trench feature profile can be fabricated by controlling the bias-supply timing.

DOI： 10.1016/j.apsusc.2023.157981

An approach to reduce surface charging with cryogenic plasma etching using hydrogen-fluoride contained gases 査読有り

Hsiao S.N., Sekine M., Ishikawa K., Iijima Y., Ohya Y., Hori M.

Applied Physics Letters 123 巻 ( 21 ) 頁： 1 - 4 2023年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Letters

The surface conductivity influences the etched pattern profiles in the plasma process. In the dielectric film etching, it is vital to reduce the charging build-up, which bends the trajectory of incoming ions for highly anisotropic etching. A significant increase in surface electric conductivity of SiO<inf>2</inf> films was observed when exposed to down-flow plasmas containing hydrogen fluoride (HF) at cryogenic temperature (−60 °C). This phenomenon can be attributed to two factors: (i) the absorption of HF and/or its compounds and (ii) the presence of H<inf>2</inf>O, which is likely originating from the etching by-product of SiO<inf>2</inf> and/or within the reactor. Comparing the surface electric resistance of the samples treated with HF plasmas to that of CF<inf>4</inf>/H<inf>2</inf> and C<inf>4</inf>F<inf>8</inf>/H<inf>2</inf> plasmas, we found that HF plasma treatment enables to be approximately three and six orders of magnitude lower. By using in situ x-ray photoemission spectroscopy, it was revealed that the presence of HF and/or its compounds and H<inf>2</inf>O were absorbed on the sample surface at −60 °C. These results strongly suggest that the cryogenic plasma etching with HF-contained gases can be used to alleviate the charge build-up issues.

DOI： 10.1063/5.0173553

Gas-phase study of the behavior of trimethyl gallium and triethyl gallium by optical emission spectroscopy and quadrupole mass spectroscopy for the growth of GaN by REMOCVD (radical-enhanced metalorganic chemical vapor deposition) 査読有り Open Access

Dhasiyan, AK; Jayaprasad, S; Amalraj, FW; Shimizu, N; Oda, O; Ishikawa, K; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 62 巻 ( SN ) 頁： SN1019 2023年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Metal-organic CVD (MOCVD) is a well-established means of epitaxial growth of III-nitrides in terms of production. To overcome the drawbacks of MOCVD, we have developed a radical-enhanced MOVCVD (REMOCVD) technique which is promising to grow group-III nitride materials at lower temperatures without ammonia gas. The gas phase behavior of trimethyl gallium (TMG) and triethyl gallium (TEG) in the chamber is studied with optical emission spectroscopy (OES) and quadrupole mass spectroscopy. From OES results, it is found that the parasitic reactions due to activated Ga and CN could be avoided by introducing hydrogen as a source gas together with nitrogen gas. The TEG is completely decomposed in REMOCVD at 550 °C which is a much lower temperature compared to TMG in a hydrogen atmosphere. Also, it is found that due to the low decomposition temperature of TEG, TEG contaminated the gas line which needs to be cleaned often.

DOI： 10.35848/1347-4065/acfd34

Deposition of carbon-based materials directly on copper foil and nickel foam as 2D-and 3D-networked metal substrates by in-liquid plasma 査読有り Open Access

Dela Vega, MSDC; Nguyen, TTN; Kondo, H; Tsutsumi, T; Ishikawa, K; Hori, M

PLASMA PROCESSES AND POLYMERS 20 巻 ( 11 ) 頁： 1 - 5 2023年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

In-liquid plasma (ILP) process has been an attractive route for nanomaterial synthesis due to its high-yield production in low-temperature atmospheric pressure conditions. In comparison with conventional ILP synthesis that produces free-standing nanomaterials, this work brings a new perspective on the application of the ILP process through carbon formation directly on ethanol-immersed two-dimensional (foil) and three-dimensional (3D) (foam) metal substrates. Three types of carbon, including graphene, graphitic carbon, and amorphous carbon, were simultaneously produced during plasma discharge. Graphitic and amorphous carbon formed radially and coexisted on the metal substrate surface, while free-standing graphene was produced in ethanol. A conformal coating was achieved on the exterior surface of the 3D-networked substrate. The proposed mechanism for carbon formation on metal substrates is presented here.

DOI： 10.1002/ppap.202300036

低温プラズマおよびハイパーサーミア併用効果を用いたがん治療の可能性 Open Access

橋爪博司, 近藤隆, 田中宏昌, 石川健治, 堀勝, 齋藤淳一

Thermal Medicine 39 巻 ( 3 ) 頁： 21 - 30 2023年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：日本ハイパーサーミア学会

プラズマは固体・液体・気体に続く物質の第4の状態である．狭義のプラズマは，気体を構成する分子が電離し，陽イオンと電子に分かれて運動している状態であり，電離気体に相当する．いわゆる熱プラズマはすでに消化管や鼻腔表面の組織凝固壊死を誘導する熱凝固装置治療に使われている．近年，低温プラズマ技術の発展が目覚ましく，止血，がん治療，遺伝子・薬物導入，殺菌・滅菌，創傷治療等，多くの医療分野への利用が注目されている．低温大気圧プラズマは水溶液中には多量の活性種を生成する．但し，直接照射の場合の課題はその深達性にある．そこで，我々はハイパーサーミアの併用により大気圧プラズマ誘発活性種がより多く細胞内に導入されることを期待してアポトーシスを指標にその増強効果を検討した．　実験にはヒトリンパ腫細胞株であるU937細胞を用いた．プラズマにはHeプラズマを用いた．その結果，単独では細胞致死効果を示さない42 ℃の温熱処理を付加することでプラズマ併用により相乗的なアポトーシスの増強効果が得られた．同時に細胞内活性酸素種も増加した．単独では致死効果が十分でない場合でもハイパーサーミアを付加することで細胞内への活性酸素種の導入が増え，致死効果の増強に寄与したものと思われる．　最近，プラズマ照射された溶液の生物作用が注目されている．プラズマ活性培養液やプラズマ活性乳酸リンゲル液のがん細胞致死効果が注目されている．これらプラズマ活性化溶液と温熱処理は細胞内に酸化ストレス誘導をすることが知られており，ハイパーサーミアとの併用による相乗効果が期待される．本稿ではプラズマを用いたがん治療の現状について解説するともにハイパーサーミア併用の有用性について言及する．

DOI： 10.3191/thermalmed.39.21

Development of an experimental system for cell viability assays of yeasts using gas-temperature controllable plasma jets 査読有り Open Access

Yoshimura, S; Otsubo, Y; Yamashita, A; Johzuka, K; Tsutsumi, T; Ishikawa, K; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 62 巻 ( SL ) 2023年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The characteristics of a gas-temperature-controllable atmospheric-pressure helium plasma jet and the development of an experimental system for cell viability assays of yeasts (fission yeast Schizosaccharomyces pombe and budding yeast Saccharomyces cerevisiae) are reported. The physicochemical properties of the plasma plume, which can maintain the temperature of the irradiated object at a temperature suitable for yeast, were not significantly different from those of a typical helium plasma jet. Furthermore, good reproducibility of cell viability was observed when gas temperature, gas flow rate, applied high voltage, and irradiation distance remained fixed, and only irradiation time was used as a parameter. This experimental system allows us to carry out various experiments, such as the search for plasma-resistant mutants that will contribute to the identification of genes involved in resistance to direct plasma irradiation.

DOI： 10.35848/1347-4065/acd4ca

Organic decomposition and synthesis reactions in lactated solution exposed to nonequilibrium atmospheric pressure plasma 査読有り Open Access

Liu, Y; Ishikawa, K; Tanaka, H; Miron, C; Kondo, T; Nakamura, K; Mizuno, M; Kajiyama, H; Toyokuni, S; Hori, M

PLASMA PROCESSES AND POLYMERS 20 巻 ( 5 ) 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

Lactate is used in the food and pharmaceutical industries and is a crucial intermediate for synthesis. Plasma-activated lactate (PAL) in Ringer's solution was recently shown to have effective antitumor action. Small molecule aldehydes, ketones, and organic acids were produced from lactate during plasma exposure, and five-membered conjugated lactone isomers of furanone (C<inf>5</inf>H<inf>6</inf>O<inf>2</inf>) were detected formed by interactions of lactate or its fragments with •OH, organic radicals, and H<inf>2</inf>O<inf>2</inf>. 2,3-Dimethyl-tartaric acid may be the effective component in PAL for the selective killing of cancer but not normal cells and possible pathways for its synthesis are provided. Aqueous reaction mechanisms are explained, including dehydration, esterification, hydrolysis, and dimerization. This study will help develop novel cancer therapies and further plasma organic chemistry.

DOI： 10.1002/ppap.202200193

Manipulation of etch selectivity of silicon nitride over silicon dioxide to a-carbon by controlling substate temperature with a CF4/H2 plasma 査読有り

Leukocyte Depletion and Size-Based Enrichment of Circulating Tumor Cells Using a Pressure-Sensing Microfiltration Device 査読有り Open Access

Onoshima, D; Hase, T; Kihara, N; Kuboyama, D; Tanaka, H; Ozawa, N; Yukawa, H; Sato, M; Ishikawa, K; Hasegawa, Y; Ishii, M; Hori, M; Baba, Y

ACS MEASUREMENT SCIENCE AU 3 巻 ( 2 ) 頁： 113 - 119 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Measurement Science Au

Considering the challenges in isolating circulating tumor cells (CTCs) pertaining to cellular stress and purity, we report the application of a blood microfiltration device as an optimal approach for noninvasive liquid biopsy to target CTCs. We experimentally analyzed the filtration behavior of the microfilter using pressure sensing to separate tumor cells from leukocytes in whole blood. This approach achieved an average recovery of >96% of the spiked tumor cells and depletion of >99% of total leukocytes. Furthermore, we carried out genomic profiling of the CTCs using the blood microfiltration device. The method was also applied in a clinical setting; DNA amplification was performed using a small number of microfiltered CTCs and epidermal growth factor receptor mutations were successfully detected to characterize the efficacy of molecularly targeted drugs against lung cancer. Overall, the proposed method can provide a tool for evaluating efficient filtration pressure to concentrate CTCs from whole blood.

DOI： 10.1021/acsmeasuresciau.2c00057

Hsiao, SN; Britun, N; Nguyen, TTN; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

VACUUM 210 巻頁： 111863 - 111863 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Vacuum

The effects of substrate temperature (T<inf>s</inf>) on the etch rate (ER) of the PECVD-prepared SiN, SiO<inf>2</inf> and amorphous carbon (a-C) films, and their selectivity were investigated with a CF<inf>4</inf>/H<inf>2</inf> plasma. The ERs for the SiN at all T<inf>s</inf> were higher than that for the SiO<inf>2</inf> films. As T<inf>s</inf> was decreased from 50 to −20 °C, the ER for the SiN decreased. Contrarily, the ER of the SiO<inf>2</inf> films increased. The etching selectivity of SiN over SiO<inf>2</inf> reached to near unity when the T<inf>s</inf> was −20 °C. At the same time, the ER of for the a-C films was found to be around 0.1 nm/s and irrespective of T<inf>s</inf>. The fluorocarbon (FC) thickness was greater for the SiO<inf>2</inf> films than that of the SiN. The lower ER for the SiO<inf>2</inf> was therefore attributed to the thicker FC layer and resultant etching mechanism. As the T<inf>s</inf> was decreased, the FC thickness on the SiO<inf>2</inf> films decreased, which led to the ER decrease. The decrease of ER for the SiN etching at the low temperature was likely due to the higher stability of the surface N–H modification layer, compared with that processed at 20 °C, which was confirmed by the in situ FTIR.

DOI： 10.1016/j.vacuum.2023.111863

Efficacy of periodic cold plasma treatment in a paddy to produce white-core grains in brewer's rice cultivar Yamadanishiki 査読有り

High-performance glass filters for capturing and culturing circulating tumor cells and cancer-associated fibroblasts 査読有り Open Access

Tanaka, H; Iwata, D; Shibata, Y; Hase, T; Onoshima, D; Yogo, N; Shibata, H; Sato, M; Ishikawa, K; Nagasawa, I; Hasegawa, Y; Ishii, M; Baba, Y; Hori, M

SCIENTIFIC REPORTS 13 巻 ( 1 ) 頁： 4130 2023年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Various liquid biopsy methods have been developed for the non-invasive and early detection of diseases. In particular, the detection of circulating tumor cells (CTCs) and cancer-associated fibroblasts (CAFs) in blood has been receiving a great deal of attention. We have been developing systems and materials to facilitate such liquid biopsies. In this study, we further developed glass filters (with various patterns of holes, pitches, and non-adhesive coating) that can capture CTCs, but not white blood cells. We optimized the glass filters to capture CTCs, and demonstrated that they could be used to detect CTCs from lung cancer patients. We also used the optimized glass filters for detecting CAFs. Additionally, we further developed a system for visualizing the captured cells on the glass filters. Finally, we demonstrated that we could directly culture the captured cells on the glass filters. Based on these results, our high-performance glass filters appear to be useful for capturing and culturing CTCs and CAFs for further examinations.

DOI： 10.1038/s41598-023-31265-9

Generation and measurement of low-temperature plasma for cancer therapy: a historical review 査読有り Open Access

Ishikawa, K; Takeda, K; Yoshimura, S; Kondo, T; Tanaka, H; Toyokuni, S; Nakamura, K; Kajiyama, H; Mizuno, M; Hori, M

FREE RADICAL RESEARCH 57 巻 ( 3 ) 頁： 239 - 270 2023年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Free Radical Research

This review provides a description of the historical background of the development of biological applications of low-temperature plasmas. The generation of plasma, methods and devices, plasma sources, and measurements of plasma properties, such as electron dynamics and chemical species generation in both gaseous and aqueous phases, were assessed. Currently, direct irradiation methods for plasma discharges contacting biological surfaces, such as the skin and teeth, are related to plasma biological interactions. Indirect methods using plasma-treated liquids are based on plasma–liquid interactions. The use of these two methods is rapidly increasing in preclinical studies and cancer therapy. The authors address the prospects for further developments in cancer therapeutic applications by understanding the interactions between the plasma and living organisms.

DOI： 10.1080/10715762.2023.2230351

Hashizume, H; Kitano, H; Mizuno, H; Abe, A; Yuasa, G; Tohno, S; Tanaka, H; Ishikawa, K; Matsumoto, S; Sakakibara, H; Hirosue, Y; Maeshima, M; Mizuno, M; Hori, M

FREE RADICAL RESEARCH 57 巻 ( 3 ) 頁： 161 - 173 2023年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Free Radical Research

We investigated the effect of cold plasma application on the yield and grain quality of rice (Oryza sativa L.), focusing on the brewer’s rice cultivar, Yamadanishiki. Two treatment methods were examined in a paddy; direct plasma irradiation of seedlings and indirect treatment with plasma-activated Ringer’s lactate solution (PAL) during the vegetative growth phase. Periodic direct irradiation for 30 s increased whole plant weight and grain yield. Treatment with PAL promoted some growth of panicles relatively and partially suppressed the growth of culms and leaves. Both treatments affected the grain quality; an increase of the ratio of white-core grains to total number of grains, which is suited for producing Japanese sake rice, as well as a decrease of the ratio of immature grains. The results showed that the effective production of rice grains for sake production can be improved by the application of cold plasma treatment of rice seedlings in a paddy.Highlight Rice plants of brewer’s rice cultivar in a paddy were treated with cold plasma, by the direct irradiation of plants and the immersed of plants in plasma-activated Ringer’s lactate (PAL). Direct plasma irradiation promoted plant weight, grain ripening, and increased yield. PAL treatment affected the growth of main stem and promoted the growth of panicles relatively. Both treatments improved the producing white-core grains, in addition to promotion of grain ripening. Cold plasma treatment can be applied to produce stable and high-quality food in various agriculture and food industries, which can achieve the sustainable developmental goals (SDGs).

DOI： 10.1080/10715762.2023.2215914

Cancer-specific cytotoxicity of Ringer's acetate solution irradiated by cold atmospheric pressure plasma 査読有り Open Access

Miron, C; Ishikawa, K; Kashiwagura, S; Suda, Y; Tanaka, H; Nakamura, K; Kajiyama, H; Toyokuni, S; Mizuno, M; Hori, M

FREE RADICAL RESEARCH 57 巻 ( 2 ) 頁： 91 - 104 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Free Radical Research

Cold atmospheric pressure plasmas are promising medical tools that can assist in cancer treatment. While the medical pathology mechanism is substantially understood, knowledge of the contribution of reactive species formed in plasma and the mode of activation of biochemical pathways is insufficient. Herein, we present a concept involving antitumoral plasma-activated organics, which is envisaged to increase cytotoxicity levels against cancer cells. Ringer′s acetate solution was irradiated by low-temperature plasma at atmospheric pressure and possible reaction pathways of the compound generation are presented. The chemical compounds formed by plasma treatment and their effects on non-tumorigenic breast epithelial cells (MCF-10A) and breast cancer cells (MCF-7) were investigated. The cell viability results have shown that plasma-derived compounds have both, stimulatory and inhibitory effects on cell viability, depending on the concentration of the generated compounds in the irradiated liquids. Previous studies have shown that oxidative stresses involving reactive oxygen and nitrogen species (RONS) can be used to kill cancer cells. Hence, while RONS offers promising first-step killing effects, cell viability results have shown that plasma-derived compounds, such as acetic anhydride and ethyl acetate, have the potential to play important roles in plasma-based cancer therapy.

DOI： 10.1080/10715762.2023.2201390

Plasma-Assisted Priming: Improved Germination and Seedling Performance of Papaya 査読有り Open Access

Xi, DK; Yap, SL; Kumar, NN; Toh, CC; Ishikawa, K; Hori, M

SAINS MALAYSIANA 52 巻 ( 2 ) 頁： 599 - 611 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Sains Malaysiana

Papaya is a one of the important tropical fruit crops with a global export of 353 ktonnne reported in 2020. The germination of papaya seed is erratic and often non-uniform. Plasma assisted priming of seed was performed at atmospheric pressure in a parallel plate dielectric barrier discharge system. The germination rate of papaya seeds and the growth performance of the seedling were monitored for several treatment plans combining the atmospheric pressure plasma treatment with soaking of seed in deionized water. An enhanced germination rate of 92% was obtained by the plasma assisted priming, compared to the untreated of 60%. The plasma assisted priming performed by plasma treatment and soaking in an opposite sequence showed different requirement and possibly involved different mechanisms. The treatment time was reduced to only 4 minutes for pre-soaked seeds, otherwise the germination rate increased with the plasma treatment time from 3 to 30 min treatment. The plasma assisted priming approaches were also found enhancing seedling growth performance. The treated seedling grows about two times bigger and the dried mass measured after 30 days was more than 100% compared to that of the untreated and hot water treated seeds.

DOI： 10.17576/jsm-2023-5202-21

Cooperation of Poly(rC)-binding Proteins 1/2 and Glutathione in Ferroptosis Induced by Plasma-activated Ringer's Lactate 査読有り

Zheng, H; Jiang, L; Lyu, QY; Akatsuka, S; Motooka, Y; Sekido, Y; Nakamura, K; Tanaka, H; Ishikawa, K; Kajiyama, H; Mizuno, M; Hori, M; Toyokuni, S

CANCER SCIENCE 114 巻頁： 749 - 749 2023年2月

Cooperation of Poly(rC)-binding Proteins 1/2 and Glutathione in Ferroptosis Induced by Plasmaactivated Ringer's Lactate 査読有り

Zheng, H; Jiang, L; Lyu, QY; Akatsuka, S; Motooka, Y; Sekido, Y; Nakamura, K; Tanaka, H; Ishikawa, K; Kajiyama, H; Mizuno, M; Hori, M; Toyokuni, S

CANCER SCIENCE 114 巻頁： 1340 - 1340 2023年2月

GaN damage-free cyclic etching by sequential exposure to Cl2 plasma and Ar plasma with low Ar+-ion energy at substrate temperature of 400 °C 査読有り国際誌

Nakamura, S; Tanide, A; Kimura, T; Nadahara, S; Ishikawa, K; Oda, O; Hori, M

JOURNAL OF APPLIED PHYSICS 133 巻 ( 4 ) 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

Damage-free atomic layer etching (ALE) of GaN was demonstrated using a cyclic process in which the chlorinated layer formed by Cl2 plasma exposure was removed by exposure to Ar plasma with energy-controlled ions when the substrate temperature was maintained at 400 °C. The layer chlorinated at 400 °C by Cl2 plasma exposure was found to be thinner than that chlorinated at 25 °C. Therefore, in the case of an Ar+-ion energy of 70 eV, the "ALE synergy"parameter, which quantifies the degree to which a process approaches the ideal ALE regime, decreased from 86% at a substrate temperature of 25 °C to 24% at a substrate temperature of 400 °C. A substrate temperature of 400 °C promoted etching even at the lower ion energy of 40 eV, thereby resulting in a higher ALE synergy of 62%. The vertical etching profile with no degradation of photoluminescence near the band edge on the etched surface was then observed. The proposed high-temperature ALE method is promising for realizing a vertical pattern profile via damage-free etching of GaN.

DOI： 10.1063/5.0131685

Mechanical properties of maze-like carbon nanowalls synthesized by the radial injection plasma enhanced chemical vapor deposition method 査読有り Open Access

Ghodke, S; Murashima, M; Christy, D; Van Nong, N; Ishikawa, K; Oda, O; Umehara, N; Hori, M

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 862 巻 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering A

The unique structural properties of vertically aligned graphene sheets or Carbon Nanowalls (CNWs) have attracted great interests for their potential for various applications in microelectronic devices, energy storage, and catalyst support materials. During the handling or operation of the devices, tension and/or pressure are often needed. Under such conditions, CNWs must undergo compression and stress. Therefore, the deformation mechanism and evolution behavior of the CNW structures under load play a critical role in the performance and reliability of the devices. In this study, the mechanical properties of a typical maze-like CNW structure synthesized by a Radial Injection Plasma Enhanced Chemical Vapor Deposition (RI-PECVD) technique were analyzed by employing the nanoindentation method. The measured compressive strength of the CNW structure was 50 MPa with an average modulus E value of ∼28 GPa, which is significantly higher than that of pyrolytic graphite and other graphene-based materials such as 3D graphene-derived carbon, commercial graphene, and reduced graphene oxide films. An elastoplastic behavior of a soft material was observed in high-resolution microscopy and a mechanism of deformation for CNWs is elucidated.

DOI： 10.1016/j.msea.2022.144428

Effects of plasma-activated Ringer's lactate solution on cancer cells: evaluation of genotoxicity 査読有り Open Access

Liu, Y; Nakatsu, Y; Tanaka, H; Koga, K; Ishikawa, K; Shiratani, M; Hori, M

GENES AND ENVIRONMENT 45 巻 ( 1 ) 頁： 3 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Genes and Environment

Background: Non-thermal atmospheric pressure plasma technologies form the core of many scientific advances, including in the electronic, industrial, and biotechnological fields. The use of plasma as a cancer therapy has recently attracted significant attention due to its cancer cell killing activity. Plasma-activated Ringer’s lactate solution (PAL) exhibits such activity. In addition to ROS, PAL contains active compounds or species that cause cancer cell death, but the potential mutagenic risks of PAL have not been studied. Results: PAL has a low pH value and a high concentration of H<inf>2</inf>O<inf>2</inf>. H<inf>2</inf>O<inf>2</inf> was removed from PAL using catalase and catalase-treated PAL with a pH of 5.9 retained a killing effect on HeLa cells whereas this effect was not observed if the PAL was adjusted to pH 7.2. Catalase-treated PAL at pH 5.9 had no significant effect on mutation frequency, the expression of γH2AX, or G2 arrest in HeLa cells. Conclusion: PAL contains one or more active compounds or species in addition to H<inf>2</inf>O<inf>2</inf> that have a killing effect on HeLa cells. The compound(s) is active at lower pH conditions and apparently exhibits no genotoxicity. This study suggested that identification of the active compound(s) in PAL could lead to the development of novel anticancer drugs for future cancer therapy.

DOI： 10.1186/s41021-023-00260-x

Editorial: Prospects of plasma generated species interaction with organic and inorganic materials 査読有り Open Access

Attri, P; Koga, K; Kurita, H; Ishikawa, K; Shiratani, M

FRONTIERS IN PHYSICS 10 巻 2023年1月

Plasma activated Ringer's lactate solution 査読有り Open Access

Tanaka, H; Mizuno, M; Ishikawa, K; Miron, C; Okazaki, Y; Toyokuni, S; Nakamura, K; Kajiyama, H; Hori, M

FREE RADICAL RESEARCH 57 巻 ( 1 ) 頁： 14 - 20 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Free Radical Research

Low-temperature plasma (LTP) has been widely used in life science. Plasma-activated solutions were defined as solutions irradiated with LTP, and water, medium, and Ringer’s solutions have been irradiated with LTP to produce plasma-activated solutions. They contain chemical compounds produced by reactions among LTP, air, and solutions. Reactive oxygen and nitrogen species (RONS) are major components in plasma-activated solutions and recent studies revealed that plasma-activated organic compounds are produced in plasma-activated Ringer’s lactate solution (PAL). Many in vitro and in vivo studies demonstrated that PAL exhibits anti-tumor effects on cancers, and biochemical analyses revealed intracellular molecular mechanisms of cancer cell death by PAL.

DOI： 10.1080/10715762.2023.2182663

Biocompatibility of conformal silicon carbide on carbon nanowall scaffolds 査読有り Open Access

Ono, K; Koide, T; Ishikawa, K; Tanaka, H; Kondo, H; Sugawara-Narutaki, A; Jin, Y; Yasuhara, S; Hori, M; Takeuchi, W

JAPANESE JOURNAL OF APPLIED PHYSICS 62 巻 ( SA ) 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Silicon carbide (SiC) was coated onto carbon nanowall (CNW) scaffolds using chemical vapor deposition with a vinylsilane precursor at 700 °C to investigate the influence of the wall edge width, wall-to-wall distance, and surface morphology. The wall edge width ranged from 10 nm to those filling the wall-to-wall space without disrupting the CNW morphology. When SiC-coated CNWs (SiC/CNWs) were used as scaffolds for cell culture, cell viability increased until the edge area ratio reached 40%. In over 40% of edge area ratio, cell viability was saturate and comparable to flat surfaces such as SiC films on the Si substrate (SiC/Si) and control samples prepared using polystyrene. Calcification was suppressed in the CNWs, SiC/CNWs, and SiC/Si scaffolds compared to polystyrene. Our results suggest that SiC-coated CNW scaffolds could suppress calcification and promote cell proliferation.

DOI： 10.35848/1347-4065/ac9319

Science-based, data-driven developments in plasma processing for material synthesis and device-integration technologies 査読有り国際共著国際誌 Open Access

Kambara, M; Kawaguchi, S; Lee, HJ; Ikuse, K; Hamaguchi, S; Ohmori, T; Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 62 巻 ( SA ) 頁： SA0803 2023年1月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Low-temperature plasma-processing technologies are essential for material synthesis and device fabrication. Not only the utilization but also the development of plasma-related products and services requires an understanding of the multiscale hierarchies of complex behaviors of plasma-related phenomena, including plasma generation in physics and chemistry, transport of energy and mass through the sheath region, and morphology- and geometry-dependent surface reactions. Low-temperature plasma science and technology play a pivotal role in the exploration of new applications and in the development and control of plasma-processing methods. Presently, science-based and data-driven approaches to control systems are progressing with the state-of-the-art deep learning, machine learning, and artificial intelligence. In this review, researchers in material science and plasma processing, review and discuss the requirements and challenges of research and development in these fields. In particular, the prediction of plasma parameters and the discovery of processing recipes are asserted by outlining the emerging science-based, data-driven approaches, which are called plasma informatics.

DOI： 10.35848/1347-4065/ac9189

Effects of High-Quality Carbon Nanowalls Ionization-Assisting Substrates on Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Performance 査読有り Open Access

Sakai, R; Kondo, H; Ishikawa, K; Ohta, T; Hiramatsu, M; Tanaka, H; Hori, M

NANOMATERIALS 13 巻 ( 1 ) 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nanomaterials

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is performed using carbon nanowalls (CNWs) for ionization-assisting substrates. The CNWs (referred to as high-quality CNWs) in the present study were grown using a radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD) system with the addition of oxygen in a mixture of CH<inf>4</inf> and H<inf>2</inf> gases. High-quality CNWs were different with respect to crystallinity and C–OH groups, while showing similar wall-to-wall distances and a wettability comparable to CNWs (referred to as normal CNWs) grown without O<inf>2</inf>. The efficiency of SALDI was tested with both parameters of ion intensity and fragmental efficiency (survival yield (SY)) using N-benzylpyridinuim chloride (N-BP-CI). At a laser fluence of 4 mJ/cm2, normal CNWs had an SY of 0.97 and an ion intensity of 0.13, while 5-sccm-O<inf>2</inf>– high-quality CNWs had an SY of 0.89 and an ion intensity of 2.55. As a result, the sensitivity for the detection of low-molecular-weight analytes was improved with the high-quality CNWs compared to the normal CNWs, while an SY of 0.89 was maintained at a low laser fluence of 4 mJ/cm2. SALDI-MS measurements available with the high-quality CNWs ionization-assisting substrate provided high ionization and SY values.

DOI： 10.3390/nano13010063

Selective isotropic atomic-layer etching of thin films by using dry chemical removal tool 査読有り

Shinoda K., Miyoshi N., Kobayashi H., Izawa M., Ishikawa K., Hori M.

Proceedings of SPIE the International Society for Optical Engineering 12499 巻 2023年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of SPIE the International Society for Optical Engineering

There has been considerable interest in the development of isotropic atomic layer etching (ALE) for the conformal removal of thin films. Material selectivity is crucial for the development of isotropic ALE because the next generation of semiconductor devices will be constructed with miniaturized 3D structures using a variety of very thin films. We developed plasma-assisted thermal-cyclic ALE, which is a repetition of surface modification by plasma exposure and removal of the modified surface by infrared heating. We developed a 300-mm tool, namely, dry chemical removal (DCR), which is equipped with an inductively coupled plasma (ICP) source and infrared lamps, to facilitate rapid thermal desorption of the modified surface. An important feature of the plasma-assisted thermal-cyclic ALE is that it has more tuning knobs than that of conventional ALE because it uses two temperatures: a low temperature for surface modification and an elevated temperature for the removal of the modified surface. This paper presents the selective ALE of various materials, i.e., Si3N4, TiN, W, and SiGe using the developed tool. The mechanisms of the selectivity are divided into two categories: formation of an ammonium salt-based modified layer and selectivity control by adjusting the infrared heating time. This paper reviews the selective ALE mechanisms, focusing on the results of in situ analysis of surface reactions, and presents some of the latest findings.

DOI： 10.1117/12.2664547

低温大気圧プラズマによるフリーラジカル生成とその生物学的意義-放射線との比較- 査読有り

近藤隆, 田中宏昌, 石川健治, 堀勝

化学工業 74 巻 ( 2 ) 頁： 120 - 126 2023年

総説：プラズマなどで処理された水の多様性査読有り

石川健治

静電気学会誌 46 巻頁： 209 2023年

Impact of microsecond-pulsed plasma-activated water on papaya seed germination and seedling growth 査読有り

Xi, DK; Zhang, XH; Yang, SZ; Yap, SS; Ishikawa, K; Hori, M; Yap, SL

CHINESE PHYSICS B 31 巻 ( 12 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chinese Physics B

The seed of Carica papaya consists of a hard shell-like testa with inhibitors in vivo causing slow, erratic and asynchronous germination. In this work, plasma-activated water prepared by microsecond-pulsed plasma jets (μPAW) was applied to treat papaya seeds. The μPAW after plasma activation of 30 min was about 40 °C. The reactive species such as NO<inf>2</inf>, NO<inf>3</inf>, and H<inf>2</inf>O<inf>2</inf> in the μPAW activated from deionized water were measured and correlated to the seed germination rate and the seedling growth performance. The μPAW-treated papaya seed achieved a higher germination rate of 90%, which is 26% higher than the control group using deionized water. Comparing the results with a hot water (40 °C) reference group showed that the reactive species in μPAW played primary roles in germination improvement, with little effect caused by the heat shock. The μPAW also sterilized the treated seeds, reducing the germination stress. The morphological change in the seeds was observed by SEM, showing an effect of physical etching after treatment promoting seed imbibition. The biochemical mechanism of the seed germination was deduced with reference to the evolution of surface chemistry, functional groups, and ABA content. The accelerated seed metabolism observed was corresponded to the chemical modification pathway. Besides, early seedlings developed from treated seeds were observed to be healthy, grow more leaves, and have better root structures. The content of MDA in the treated papaya seedlings decreased along with increased SOD and higher ion concentration. The μPAW that can be prepared at atmospheric pressure for bulk production offers a low-risk and cost-effective seed priming technology that may significantly increase the production of agricultural crops.

DOI： 10.1088/1674-1056/ac904e

Indoor Floor Heel Mark Removal Using Spark Discharges and Pressurized Airflow 査読有り Open Access

Sakamoto, Y; Tsutsumi, T; Tanaka, H; Ishikawa, K; Hashizume, H; Hori, M

COATINGS 12 巻 ( 12 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Coatings

Heel marks (HMs), which are the black stains made by shoe soles on indoor floors, can be difficult to remove. However, this study shows how spark discharges combined with pressurized airflow in 60 s discharge treatments can remove such HMs. We further show that maximizing the HM removal rates depended on the electrode gap distance because of changes in the spark discharge parameters. In our experiments, the electrical voltage waveforms are shown with voltage spikes, called spark discharges, and the spike numbers were counted in 0.6-ms time units. It was found that the number of spark discharges increases when the electrode gap distance was widened from 5 mm to 10 mm and the pressurized airflow was added, and the HM removal rates increased 11.5%, the HM removal rates could be maximized. Taken together, the results show that spark discharges combined with pressurized air can remove HMs from indoor floors without no visual damage. This paper is a preliminary report showing that HMs can be removed by plasma.

DOI： 10.3390/coatings12121938

Carbon Layer Formation on Hexagonal Boron Nitride by Plasma Processing in Hydroquinone Aqueous Solution 査読有り

Inoue, K; Sakakibara, N; Goto, T; Ito, T; Shimizu, Y; Hakuta, Y; Ishikawa, K; Hori, M; Terashima, K

ACS APPLIED MATERIALS & INTERFACES 14 巻 ( 47 ) 頁： 53413 - 53420 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Materials and Interfaces

Although hexagonal boron nitride (hBN) is a thermally conductive and electrically insulating filler in composite materials, surface modification remains difficult, which limits its dispersibility and functionalization. In this study, carbon layer formation on hBN particles by plasma processing in hydroquinone aqueous solution was investigated as a surface modification technique. Carbon components with features of polymeric hydrogenated amorphous carbon were found to be uniformly distributed on the hydroquinone-aided plasma-modified hBN (HQpBN) particles. Electron spin resonance measurements revealed abundant unpaired electrons in HQpBN, indicating that defects were formed on hBN by plasma processing and that the carbon layer contained dangling bonds. The defects on hBN could help in the attachment of the carbon layer, whereas the dangling bonds could act as reactive sites for further functionalization. The carbon layer on HQpBN was successfully functionalized with isocyanate groups, thus confirming the ability of this carbon layer to facilitate surface modification. These results demonstrate that the carbon layer formed on hBN can provide a designable interface in organic/inorganic composite materials.

DOI： 10.1021/acsami.2c15951

Dry etching of ternary metal carbide TiAlC via surface modification using floating wire-assisted vapor plasma 査読有り Open Access

Nguyen, TTN; Shinoda, K; Hamamura, H; Maeda, K; Yokogawa, K; Izawa, M; Ishikawa, K; Hori, M

SCIENTIFIC REPORTS 12 巻 ( 1 ) 頁： 20394 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Dry etching of ternary metal carbides TiAlC has been first developed by transferring from wet etching to dry etching using a floating wire (FW)-assisted Ar/ammonium hydroxide vapor plasma. FW-assisted non-halogen vapor plasma generated at medium pressure can produce high-density reactive radicals (NH, H, and OH) for TiAlC surface modifications such as hydrogenation and methylamination. A proposed mechanism for dry etching of TiAlC is considered with the formation of the volatile products from the modified layer.

DOI： 10.1038/s41598-022-24949-1

Effects of deposition precursors of hydrogenated amorphous carbon films on the plasma etching resistance based on mass spectrometer measurements and machine learning analysis 査読有り Open Access

Kurokawa, J; Kondo, H; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

VACUUM 205 巻 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Vacuum

In the growth of hydrogenated amorphous carbon (a-C:H) films by plasma enhanced chemical vapor deposition (PECVD) with H<inf>2</inf>, CH<inf>4</inf> and C<inf>3</inf>H<inf>6</inf> plasma, the gas phase reaction of active species and their contribution to properties of deposited a-C:H film were quantitatively investigated using appearance quadrupole mass spectrometry (QMS) and machine learning. The QMS measurement indicated that two-types of neutral radicals were generated by the dissociation and polymerization of the raw material gasses. A random forest regression model was employed as a prediction model to analyze the correlation between the neutral species and etching rates by molecular oxygen (O<inf>2</inf>) plasma without any stage bias, which were measured by in-situ ellipsometry. The coefficient of determination (R2), an indicator of the degree of prediction accuracy, was 0.906 and 0.584 for the training and test data, respectively. SHapley Additive exPlanations (SHAP), interpreting the random forest model, were used to quantitatively indicate the contribution of radicals to the etching rate, including their synergistic and secondary effects. They indicated that carbon-rich radicals, such as C<inf>3</inf>H<inf>3</inf> and C<inf>5</inf>H<inf>5</inf>, contributed to a decrease in the etching rate, whereas hydrogen-rich radicals, such as CH<inf>x</inf> (x=1,2,3,4), C<inf>2</inf>H<inf>5</inf>, C<inf>4</inf>H<inf>9</inf>, and C<inf>5</inf>H<inf>9,11</inf> induced an increase in the etching rate by the O<inf>2</inf> plasma. (200 words)

DOI： 10.1016/j.vacuum.2022.111351

Dissociation channels of c-C4F8 to C2F4 in reactive plasma 査読有り国際誌

Hayashi, T; Ishikawa, K; Sekine, M; Hori, M; Iwayama, H

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( 10 ) 頁： 106006 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Progress in computational methods and personal computing has made possible more accurate estimations for primary dissociation channels and energies. The main dissociation route is revealed to be via the 7E excited state with an energy of 12.23 eV, which is composed of transitions from the highest occupied molecular orbital with b1 symmetry to some degenerate unoccupied e molecular orbitals. The main contributing e orbitals consisted of antibonding combination of C2F4 π-bonding orbitals. This degenerate 7E state is lowered by non-adiabatic transitions through the conical interactions on the dissociating route to 2C2F4, so the energy is finally relaxed at the dissociative second lowest 1E excited state leading to 2C2F4 production. In the electron attachment process, the calculated results show that the F- ion is produced from the excited states of the D4h c-C4F8- ion through conical interactions at the energies of 4.3 eV, 5.6 eV, and 5.0 eV, along the C-F dissociation route.

DOI： 10.35848/1347-4065/ac895e

非平衡大気圧プラズマを用いた陸上養殖実現に向けた基礎的研究査読有り Open Access

田中宏昌, 秋山真一, 橋爪博司, 紅林佑弥, 石川健治, 堀勝

応用物理学会学術講演会講演予稿集 2022.2 巻 ( 0 ) 頁： 1741 - 1741 2022年8月

In-liquid plasma synthesis of iron-nitrogen-doped carbon nanoflakes with high catalytic activity 査読有り

Kondo, H; Hamaji, R; Amano, T; Ishikawa, K; Sekine, M; Hiramatsu, M; Hori, M

PLASMA PROCESSES AND POLYMERS 19 巻 ( 8 ) 2022年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

Flake-shaped carbon nanomaterials with nitrogen (N) and iron (Fe) addition, so-called carbon nanoflakes (CNFLs), were synthesized by the in-liquid plasma using two different kinds of additive agents, such as hemin and iron (II) phthalocyanine (FePc). According to scanning electron microscopy images and Raman spectra, CNFLs with a size of at least 100 nm order were formed regardless of types of additive agents, and crystallinity of six-membered ring structures was improved as additive agents increased. Photoelectron spectra showed that pyridinic N contents increased from 1.05% to 2.02% with increasing FePc, while those decreased from 0.34% to 0.14% with hemin. In the oxygen reduction reaction, onset potential values also increased from 0.71 to 0.79 eV with increasing FePc, while those decreased from 0.60 to 0.47 eV with hemin. These results suggested that the catalytic activity of CNFLs was effectively improved by the increase of pyridinic N by the in-liquid plasma synthesis with FePc. In contrast, the electron transfer numbers reached 3.81 when hemin increased, although those were less than 2.88 in the cases using FePc. These results mean that the in-liquid plasma synthesis method of CNFLs using FePc has the potential to further improve its catalytic activity.

DOI： 10.1002/ppap.202100203

Study of optical emission spectroscopy using modified Boltzmann plot in dual-frequency synchronized pulsed capacitively coupled discharges with DC bias at low-pressure in Ar/O2/C4F8 plasma etching process 査読有り

Dry Process

Akatsuka H., Kurihara K., Toyoda H., Karahashi K., Ishikawa K., Ichiki T., Eriguchi K., Kuboi N., Matsui M., Nunomura S.

Japanese Journal of Applied Physics 61 巻 ( SI ) 2022年7月

Sahu, BB; Nakane, K; Ishikawa, K; Sekine, M; Tsutsumi, T; Gohira, T; Ohya, Y; Ohno, N; Hori, M

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 24 巻 ( 22 ) 頁： 13883 - 13896 2022年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

We consider the corona model and local thermal equilibrium approximations of a real plasma to measure the electron temperature (T<inf>e</inf>) and density (n<inf>e</inf>), respectively, using the optical emission spectroscopy (OES) method in dual-frequency pulsed capacitively coupled plasmas (CCPs) in a reactive mixture of Ar/O<inf>2</inf>/C<inf>4</inf>F<inf>8</inf> at a low operating pressure. The operation conditions such as DC continuous and synchronized were used for the study and plasma characterization for the intended plasma application such as high aspect ratio etching (HARE). We show that the present plasma conditions are dominated by a corona balance rather than the supremacy of multi-step excitation. This fact has enabled us to utilize the modified Boltzmann plot technique to evaluate the T<inf>e</inf> values. In the second method, we simultaneously used the Boltzmann and Saha equations to determine the n<inf>e</inf> value using the line intensity ratio and the value of T<inf>e</inf>. Time-resolved measurements of T<inf>e</inf> and n<inf>e</inf> were performed for completeness, and the insight of the pulsed discharge was investigated. Time evolution of n<inf>e</inf> and T<inf>e</inf> using the OES method revealed a similar trend in the change of plasma parameters, indicating electron impact ionization during the pulse on phase. It was seen that n<inf>e</inf> in the afterglow speedily decreased within a short time of ∼5 μs. Analysis suggests the formation of afterglow plasmas, which are composed of positive and negative ions with very low electron density. The results revealed that the DC-synchronized operation could be useful for plasma application such as HARE due to different plasma characteristics. It also suggests the production of ion-ion plasmas by the effective utilization of negative ions in the afterglow phase. The corona balance condition was validated in our experiments, and the results were compared with the existing literature.

DOI： 10.1039/d2cp00289b

Low-temperature reduction of SnO2 by floating wire-assisted medium-pressure H2/Ar plasma 査読有り

Nguyen, TTN; Sasaki, M; Hsiao, SN; Tsutsumi, T; Ishikawa, K; Hori, M

PLASMA PROCESSES AND POLYMERS 19 巻 ( 6 ) 2022年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

Reduction of SnO<inf>2</inf> to form spherical Sn particles and Sn etching are obtained by floating wire (FW)-assisted medium-pressure H<inf>2</inf>/Ar plasma. High-density H<inf>2</inf>/Ar plasma (1014 cm−3) with a larger treatment area at medium pressure (10 kPa) produces a two-times higher removal rate of SnO<inf>2</inf> (0.111 mg/min) than that at atmospheric pressure with the same treatment area of 300 mm2. SnO<inf>2</inf> film is removed from the glass surface by a two-step process involving (1) reduction of SnO<inf>2</inf> by FW-H<inf>2</inf>/Ar plasma to form spherical Sn particles and (2) removal of low-contact Sn particles by water-based cleaning. High surface smoothness (roughness of 0.488 nm) and high optical transmittance (>92%) of treated samples indicate no damage compared to that of pristine quartz glass.

DOI： 10.1002/ppap.202100209

Cytotoxicity of plasma-irradiated lactate solution produced under atmospheric airtight conditions and generation of the methyl amino group 査読有り Open Access

Ito, D; Iwata, N; Ishikawa, K; Nakamura, K; Hashizume, H; Miron, C; Tanaka, H; Kajiyama, H; Toyokuni, S; Mizuno, M; Hori, M

APPLIED PHYSICS EXPRESS 15 巻 ( 5 ) 2022年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Ringer's lactate solution was irradiated with non-equilibrium plasma under airtight conditions. The plasma-activated lactate (PAL) was produced with argon, oxygen, and nitrogen gases following purging of Ar. Cytotoxicity could be controlled by diluting PAL, and a killing effect was selectively obtained on cancer cells compared to normal cells for Ar+O2+N2 PALs. Nonetheless, cytotoxicity was partly reproduced by similar concentrations of H2O2 and NO2- in the PALs. The organics produced by plasma irradiation to lactate were investigated using nuclear magnetic resonance, and the generation of methyl amino species was confirmed.

DOI： 10.35848/1882-0786/ac6360

Plasma-assisted thermal-cyclic atomic-layer etching of tungsten and control of its selectivity to titanium nitride 査読有り

Shinoda, K; Miyoshi, N; Kobayashi, H; Hanaoka, Y; Izawa, M; Ishikawa, K; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 40 巻 ( 2 ) 2022年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B

Plasma-assisted thermal-cyclic atomic-layer etching (ALE) of tungsten (W), the selectivity of which with respect to TiN can be tuned between highly selective and nonselective by changing infrared-heating time, has been demonstrated. It is a two-step process consisting of exposure to radicals generated in a CHF3/O2 or CH2F2/O2/Ar plasma followed by infrared heating. Analysis by in situ x-ray photoelectron spectroscopy confirmed that a WFx-based modified surface formed on the surface of a W film exposed to radicals at -22 °C. The modified surface on the W film is volatile at a heating temperature lower than that required for removing the modified surface on the TiN film. Cyclic etching of both W and TiN was performed by using the CH2F2/O2/Ar plasma and infrared heating in a 300-mm ALE apparatus. When the infrared-heating time was not long enough to remove the modified surface on TiN, the cyclic repetition etched only the W film. On the other hand, when the infrared-heating time was long enough to remove modified surfaces on both W and TiN, the cyclic repetition etched both W and TiN films. Therefore, both highly selective and nonselective ALEs for W and TiN were obtained by choosing an optimum infrared-heating time. This shows that material selectivity in plasma-assisted thermal-cyclic ALE can be controlled by changing the infrared-heating time.

DOI： 10.1116/6.0001660

稲穂への低温プラズマ照射がもたらす酒造品種玄米の品質向上査読有り

橋爪博司, 北野英己, 水野寛子, 蕭世男, 三田薫, 阿部明子, 東野里江, 松本省吾, 水野正明, 石川健治, 堀勝, 田中宏昌, 前島正義, 榊原均, 湯浅元気, 仁川進

応用物理学会学術講演会講演予稿集 2022.1 巻 ( 0 ) 頁： 1515 - 1515 2022年2月

C4F8/SF6ガス変調サイクルにおいてバイアス印加位相がエッチング形状に及ぼす影響査読有り

吉江泰斗, 堤隆嘉, 石川健治, 関根誠, 近藤博基, 堀勝

応用物理学会学術講演会講演予稿集 2022.1 巻 ( 0 ) 頁： 1447 - 1447 2022年2月

Ar/F2プラズマとBCl3の交互供給によるAlGaN原子層エッチングでの組成比制御査読有り

中村昭平, 木村貴弘, 谷出敦, 灘原壮一, 小田修, 堀勝, 石川健治

応用物理学会学術講演会講演予稿集 2022.1 巻 ( 0 ) 頁： 1445 - 1445 2022年2月

Scaffolds with isolated carbon nanowalls promote osteogenic differentiation through Runt-related transcription factor 2 and osteocalcin gene expression of osteoblast-like cells 査読有り Open Access

Ichikawa, T; Ishikawa, K; Tanaka, H; Shimizu, N; Hori, M

AIP ADVANCES 12 巻 ( 2 ) 2022年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Aip Advances

Carbon nanowalls (CNWs) with average wall-to-wall distances ranging from 100 to 3300 nm were synthesized using a radical injection plasma-enhanced chemical vapor deposition system. Application of a negative high voltage to the growth substrate using an inductor energy storage (IES) circuit provided CNWs with wall-to-wall distances depending on the nano-second pulse voltage of the IES circuit. Sparse isolated CNWs with average wall-to-wall distances of 700 nm were used for culturing Saos-2 cells. These cells showed better adhesion than the control after 2 days’ incubation and enhanced gene expression of the osteogenic differentiation genes Runt-related transcription factor 2 (Runx2) and osteocalcin after 10 days’ incubation. Sparse isolated CNW scaffolds hold promise for regulating the differentiation of osteoblast-like cells.

DOI： 10.1063/5.0075530

Enhancement of ethanol production and cell growth in budding yeast by direct irradiation of low-temperature plasma 査読有り Open Access

Tanaka, H; Matsumura, S; Ishikawa, K; Hashizume, H; Ito, M; Nakamura, K; Kajiyama, H; Kikkawa, F; Ito, M; Ohno, K; Okazaki, Y; Toyokuni, S; Mizuno, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( SA ) 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Ethanol production by budding yeast was compared between direct and indirect plasma irradiation. We observed enhancement of ethanol production and cell growth not by indirect plasma irradiation but by direct plasma irradiation. Glucose consumption was increased in budding yeast by direct plasma irradiation. Extracellular flux analysis revealed that glycolytic activity in the budding yeast was elevated by direct plasma irradiation. These results suggest that direct plasma irradiation enhances ethanol production in budding yeast by elevating the glycolytic activity.

DOI： 10.35848/1347-4065/ac2037

Towards prevention and prediction of infectious diseases with virus sterilization using ultraviolet light and low-temperature plasma and bio-sensing devices for health and hygiene care 査読有り国際共著 Open Access

Kumagai, S; Nishigori, C; Takeuchi, T; Bruggeman, P; Takashima, K; Takahashi, H; Kaneko, T; Choi, EH; Nakazato, K; Kambara, M; Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( SA ) 頁： SA0808 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Inspired by the ideas of many authors, we provide insight on state-of-the-art potential technologies for the prevention and prediction of infectious diseases before they spread. This review also surveys virus sterilization with ultraviolet light and low temperature plasma technologies. Researchers in the various fields of medicine, materials, electronics, and plasma sciences have addressed increasingly challenging demands and the discussion encompasses the major challenges in societies that are faced with the threat of infectious diseases. In addition, technologies that use nanomaterials are evaluated for infection prevention and hygiene purposes. Advances in biomedical diagnostics for health care in terms of complementary metal-oxide-semiconductor transistors-based devices and telemetry for health monitoring are also reviewed.

DOI： 10.35848/1347-4065/ac1c3d

Perspectives on functional nitrogen science and plasma-based in situ functionalization 査読有り Open Access

Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( SA ) 頁： SA0802 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Reactive nitrogen species (RNS) generated by controlled electron impacts in conjunction with the use of dinitrogen can react with oxygen and/or hydrogen to generate highly reactive compounds. The related field of functional nitrogen science provides new opportunities for nitrogen utilization based on non-equilibrium plasma processing. This revolutionary technique permits plasma-based nitrogen fixation at the locations at which materials such as dopants and fertilizers are required. This system, based on the in situ generation of RNS at the point of use, is expected to replace conventional processes involving nitrogen cycles employing ammonia and nitric acid. Optimization of this new approach will require nitrogen doping to be tuned by atomic-scale localization of nitrogen. This review discusses the applications of functional nitrogen and the processes by which functionalization in both inorganic materials and living organisms can occur when using RNS.

DOI： 10.35848/1347-4065/ac3558

Functional nitrogen science based on plasma processing: quantum devices, photocatalysts and activation of plant defense and immune systems 査読有り国際共著 Open Access

Kaneko, T; Kato, H; Yamada, H; Yamamoto, M; Yoshida, T; Attri, P; Koga, K; Murakami, T; Kuchitsu, K; Ando, S; Nishikawa, Y; Tomita, K; Ono, R; Ito, T; Ito, AM; Eriguchi, K; Nozaki, T; Tsutsumi, T; Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( SA ) 頁： SA0805 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Nitrogen is a very common element, comprising approximately 78% of Earth's atmosphere, and is an important component of various electronic devices while also being essential for life. However, it is challenging to directly utilize dinitrogen because of the highly stable triple bond in this molecule. The present review examines the use of non-equilibrium plasmas to generate controlled electron impacts as a means of generating reactive nitrogen species (RNS) with high internal energy values and extremely short lifetimes. These species include ground state nitrogen atoms, excited nitrogen atoms, etc. RNS can subsequently react with oxygen and/or hydrogen to generate new highly reactive compounds and can also be used to control various cell functions and create new functional materials. Herein, plasma-processing methods intended to provide RNS serving as short-lived precursors for a range of applications are examined in detail.

DOI： 10.35848/1347-4065/ac25dc

Wide range applications of process plasma diagnostics using vacuum ultraviolet absorption spectroscopy 査読有り

Takeda, K; Ishikawa, K; Hori, M

REVIEWS OF MODERN PLASMA PHYSICS 6 巻 ( 1 ) 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Reviews of Modern Plasma Physics

Applications of plasma diagnostics using vacuum ultraviolet absorption spectroscopy (VUVAS) in our studies are summarized in this article. The plasma diagnostics with absorption spectroscopy is a powerful tool for investigating behaviors of reactive species in plasma processes, because it enables us to measure the absolute density. In our group, we have focused on the clarification of reaction mechanisms of atomic species in the plasma processes, and the behaviors of atomic species generated in various process plasmas have been investigated using the VUVAS with a plasma light source. Using the VUVAS, we can investigate not only the absolute density but also surface reactions of atomic species in the plasma processes. On the other hand, in our group, the real-time monitoring of atomic species based on VUVAS has been realized in the plasma processes, and the effects of the initial state of reactor wall surface on the behaviors of atomic species in a process plasma have been quantitatively investigated. Moreover, the VUVAS has been applied to the measurements of reactive species generated by atmospheric pressure plasmas which attracts much attention because of its applications to the bio and medical research fields. These results and experimental technique used in our studies are extremely useful for the further developments of plasma processes such as etching, deposition, surface modification, bio-medical applications and so on in the future.

DOI： 10.1007/s41614-022-00075-3

Plasma Diagnostics and Characteristics of Hydrofluorocarbon Films in Capacitively Coupled CF4/H2Plasmas 査読有り

Hsiao S.N., Imai Y., Britrun N., Tsutsumi T., Ishikawa K., Sekine M., Hori M.

IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings 2022-December 巻 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings

Plasma diagnostics including electron density, temperature, neutral atomic densities of the CH4H2 plasmas were performed in a capacitively-coupled reactor using surface-wave probe, Langmuir probe and vacuum ultraviolet absorption spectroscopy. The plasma density increased monotonically with varying H2 content from 30 to 90 %. The electron temperature first decreased with H2 up to 50 % and then increased at higher H2 concentration. The HF concentration reached a maximum value at a H2 of approximately 50 %, which is probably due to balance between H and F radicals from the plasma. Increasing the H2 content resulted in a higher H concentration and a less cross-linked structure of the amorphous hydrofluorocarbon films, analyzed by using in situ Fourier transformation infrared spectroscopy.

DOI： 10.1109/ISSM55802.2022.10027112

On the Etching Mechanism of Highly Hydrogenated SiN Films by CF4/D2 Plasma: Comparison with CF4/H2 査読有り Open Access

Hsiao, SN; Nguyen, TTN; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

COATINGS 11 巻 ( 12 ) 頁： 1535 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Coatings

With the increasing interest in dry etching of silicon nitride, utilization of hydrogencontained fluorocarbon plasma has become one of the most important processes in manufacturing advanced semiconductor devices. The correlation between hydrogen-contained molecules from the plasmas and hydrogen atoms inside the SiN plays a crucial role in etching behavior. In this work, the influences of plasmas (CF<inf>4</inf>/D<inf>2</inf> and CF<inf>4</inf>/H<inf>2</inf> ) and substrate temperature (T<inf>s</inf>, from −20 to 50◦ C) on etch rates (ERs) of the PECVD SiN films were investigated. The etch rate performed by CF<inf>4</inf>/D<inf>2</inf> plasma was higher than one obtained by CF<inf>4</inf>/H<inf>2</inf> plasma at substrate temperature of 20◦ C and higher. The optical emission spectra showed that the intensities of the fluorocarbon (FC), F, and Balmer emissions were stronger in the CF<inf>4</inf>/D<inf>2</inf> plasma in comparison with CF<inf>4</inf>/H<inf>2</inf> . From X-ray photoelectron spectra, a thinner FC layer with a lower F/C ratio was found in the surface of the sample etched by the CF<inf>4</inf>/H<inf>2</inf> plasma. The plasma density, gas phase concentration and FC thickness were not responsible for the higher etch rate in the CF<inf>4</inf>/D<inf>2</inf> plasma. The abstraction of H inside the SiN films by deuterium and, in turn, hydrogen dissociation from Si or N molecules, supported by the results of in situ monitoring of surface structure using attenuated total reflectance-Fourier transform infrared spectroscopy, resulted in the enhanced ER in the CF<inf>4</inf>/D<inf>2</inf> plasma case. The findings imply that the hydrogen dissociation plays an important role in the etching of PECVD-prepared SiN films when the hydrogen concentration of SiN is higher. For the films etched with the CF<inf>4</inf>/H<inf>2</inf> at −20◦ C, the increase in ER was attributed to a thinner FC layer and surface reactions. On the contrary, in the CF<inf>4</inf>/D<inf>2</inf> case the dependence of ER on substrate temperature was the consequence of the factors which include the FC layer thickness (diffusion length) and the atomic mobility of the etchants (thermal activation reaction).

DOI： 10.3390/coatings11121535

Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF4/H2 plasma at different substrate temperatures 査読有り

プラズマがん治療招待有り査読有り

石川健治，堀勝

静電気学会誌 45 巻 ( 6 ) 頁： 206 - 212 2021年11月

Hsiao, SN; Britun, N; Nguyen, TTN; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

PLASMA PROCESSES AND POLYMERS 18 巻 ( 11 ) 頁： 2100078 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

The dependences of etching characteristics on substrate temperature (T<inf>s</inf>, from –20 to 50°C) of the plasma-enhanced chemical vapor deposition (PECVD) SiN films (PE-SiN) and low-pressure chemical vapor deposition (LPCVD) SiN films (LP-SiN) with CF<inf>4</inf>/H<inf>2</inf> plasma were investigated. The Fourier-transform infrared spectroscopy shows that both film types were N–H bond-rich films, but in different hydrogen contents (PE-SiN 22.7 at% and LP-SiN 3.8 at%) from the Rutherford backscattering spectroscopy analyses. A higher hydrogen content led to a thinner fluorocarbon thickness because of the reaction between hydrogen outflux and C and N to form an HCN byproduct. The etch rates (ER) for the PE-SiN were higher than that of the LP-SiN at all T<inf>s</inf>, due to the different FC thickness and etching mechanisms proposed. The formation of the N−H<inf>x</inf> layer on PE-SiN at low temperature caused the decrease in ER. For the LP-SiN, the weak dependences of T<inf>s</inf> on surface structure and ER were observed.

DOI： 10.1002/ppap.202100078

Plasma-activated Ringer's lactate solution inhibits the cellular respiratory system in HeLa cells 査読有り

Tanaka, H; Maeda, S; Nakamura, K; Hashizume, H; Ishikawa, K; Ito, M; Ohno, K; Mizuno, M; Motooka, Y; Okazaki, Y; Toyokuni, S; Kajiyama, H; Kikkawa, F; Hori, M

PLASMA PROCESSES AND POLYMERS 18 巻 ( 10 ) 頁： 2100056 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

Nonequilibrium atmospheric pressure plasma has enabled a variety of new applications in medicine, agriculture, and other industries. It is particularly noteworthy that plasma itself and/or plasma-activated culture medium have been shown to preferentially kill various cancer cells. We have previously developed a plasma-activated Ringer's lactate solution (PAL) for use as a new cancer treatment. In this study, behaviors of extracellular and intracellular reactive oxygen and nitrogen species in the cellular respiratory system of PAL-treated HeLa cells were investigated using an extracellular flux analyzer and a probe to measure mitochondrial membrane potential. In PAL-treated HeLa cells, extracellular hydrogen peroxide in PAL was found to be responsible for the induction of intracellular hydrogen peroxide and apoptosis, while other components in PAL are responsible for the induction of non-H<inf>2</inf>O<inf>2</inf> intracellular ROS and non-apoptotic cell death, which should be clarified by further experiments. We believe that these are long-lived species derived from plasma-activated lactates. Furthermore, we found that the plasma-activated lactates inhibited glycolysis and the tricarboxylic acid (TCA) cycle, but not the electron transport chain in HeLa cells. These results suggest that PAL induces multiple modes of cell death, including apoptosis through hydrogen peroxide, and non-apoptotic cell death associated with the impairment of mitochondrial functions (glycolysis and TCA cycle). These findings shed light on the novel mechanism underlying plasma-activated lactate-induced cell death.

DOI： 10.1002/ppap.202100056

Low temperature plasma irradiation products of sodium lactate solution that induce cell death on U251SP glioblastoma cells were identified 査読有り Open Access

Tanaka, H; Hosoi, Y; Ishikawa, K; Yoshitake, J; Shibata, T; Uchida, K; Hashizume, H; Mizuno, M; Okazaki, Y; Toyokuni, S; Nakamura, K; Kajiyama, H; Kikkawa, F; Hori, M

SCIENTIFIC REPORTS 11 巻 ( 1 ) 頁： 18488 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Low-temperature plasma is being widely used in the various fields of life science, such as medicine and agriculture. Plasma-activated solutions have been proposed as potential cancer therapeutic reagents. We previously reported that plasma-activated Ringer’s lactate solution exhibited selective cancer-killing effects, and that the plasma-treated L-sodium lactate in the solution was an anti-tumor factor; however, the components that are generated through the interactions between plasma and L-sodium lactate and the components responsible for the selective killing of cancer cells remain unidentified. In this study, we quantified several major chemical products, such as pyruvate, formate, and acetate, in plasma-activated L-sodium lactate solution by nuclear magnetic resonance analysis. We further identified novel chemical products, such as glyoxylate and 2,3-dimethyltartrate, in the solution by direct infusion-electrospray ionization with tandem mass spectrometry analysis. We found that 2,3-dimethyltartrate exhibited cytotoxic effects in glioblastoma cells, but not in normal astrocytes. These findings shed light on the identities of the components that are responsible for the selective cytotoxic effect of plasma-activated solutions on cancer cells, and provide useful data for the potential development of cancer treatments using plasma-activated L-sodium lactate solution.

DOI： 10.1038/s41598-021-98020-w

先端デバイス構造を実現する超絶ドライエッチング技術の最前線おわりに招待有り査読有り

石川健治，竹田圭吾

プラズマ核融合学会誌 97 巻 ( 9 ) 頁： 534 - 536 2021年9月

Effects of free radicals generated by atmospheric pressure plasma on physical actions and biochemical relaxations (PACR) 招待有り査読有り

石川健治, 橋爪博司, ミロンカメリア, 田中宏昌, 堀勝

放射線生物研究 56 巻 ( 3 ) 頁： 280 - 294 2021年9月

窒化物半導体プラズマエッチングにおける原子層反応制御と低ダメージプロセス招待有り査読有り

堤隆嘉，石川健治，近藤博基，関根誠，堀勝

プラズマ核融合学会誌 97 巻 ( 9 ) 頁： 517 - 521 2021年9月

先端デバイス構造を実現する超絶ドライエッチング技術の最前線はじめに招待有り査読有り

石川健治，竹田圭吾

プラズマ核融合学会誌 97 巻 ( 9 ) 頁： 508 - 510 2021年9月

Novel Method of Rebound Tailing Pulse (RTP) for Water Dissociation 査読有り

Shimizu, N; Borude, RR; Tanaka, R; Ishikawa, K; Oda, O; Hosoe, H; Ino, S; Inoue, Y; Hori, M

IEEE TRANSACTIONS ON PLASMA SCIENCE 49 巻 ( 9 ) 頁： 2893 - 2900 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Transactions on Plasma Science

Simple low-temperature pulsed power dissociation method for high resistive liquid is proposed in this article. Active high voltage rebound tailing pulse (RTP) diodes are adopted to conventional high voltage pulse power sources. In order to explain this method, the study was performed using deionized water (DIW) (high resistive >17MΩcm) electrolysis with two immersed electrodes. The forward pulses, the full-width at half-maximum (FWHM) of 400 ns and forward voltage (7 kV) with rising-up ratio (dV/dt) of 1011 V/s, were applied to the electrodes. When a 5 kV RTP diode was simply adopted to this electrical circuit and DIW load in series, the high forward voltage pulse and continuous high reverse current were applied to this circuit. Then, H2 was generated at the anode electrode and OH radical (OH) in the water vessel. Those phenomena were apparently dependent on the anode electrode area. At the beginning of the forwarded high voltage application, the circuit behaved as capacitance load with generated ions and built up charges at the interface between DIW and the electrode. Continuous rebounded high reverse voltage and highly built-up reverse recovery charges induce avalanche breakdown of RTP diode. The rebounded electrical current was found to be collected in the circuit, accompanied by the generation of hydrogen and OH, as well as the tailing current flowing at the interface as a resistive load. In consequence, we point out that rebounded electrons injected from the surrounding water to the anode electrode interface induced the water electrolysis characteristically, according to RTP-diode inserted in the circuit.

DOI： 10.1109/TPS.2021.3102639

酸素ラジカル照射したl-トリプトファン溶液の殺菌効果査読有り

石川健治, 堀勝, 伊藤昌文, 岩田直幸, 田中宏昌, 橋爪博司

応用物理学会学術講演会講演予稿集 2021.2 巻 ( 0 ) 頁： 1677 - 1677 2021年8月

低温プラズマ照射した養殖餌料アルテミアの成長促進査読有り

堀勝, 山内拓海, 石川健治, 田中宏昌, 秋山真一, 橋爪博司

応用物理学会学術講演会講演予稿集 2021.2 巻 ( 0 ) 頁： 1693 - 1693 2021年8月

原子層エッチングの反応素過程とその設計、制御査読有り

石川健治, Nguyen Thi-Thuy-Nga, 堤隆嘉, 蕭世男, 関根誠, 堀勝, 近藤博基

応用物理学会学術講演会講演予稿集 2021.2 巻 ( 0 ) 頁： 120 - 120 2021年8月

Lysosomal nitric oxide determines transition from autophagy to ferroptosis after exposure to plasma-activated Ringer's lactate 査読有り Open Access

Jiang, L; Zheng, H; Lyu, QY; Hayashi, S; Sato, K; Sekido, Y; Nakamura, K; Tanaka, H; Ishikawa, K; Kajiyama, H; Mizuno, M; Hori, M; Toyokuni, S

REDOX BIOLOGY 43 巻頁： 101989 2021年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Redox Biology

Non-thermal plasma (NTP), an engineered technology to generate reactive species, induces ferroptosis and/or apoptosis specifically in various-type cancer cells. NTP-activated Ringer's lactate (PAL) is another modality for cancer therapy at preclinical stage. Here we found that PAL induces selective ferroptosis of malignant mesothelioma (MM) cells, where non-targeted metabolome screening identified upregulated citrulline-nitric oxide (.NO) cycle as a PAL target .NO probe detected biphasic peaks transiently at PAL exposure with time-dependent increase, which was responsible for inducible .NO synthase (iNOS) overexpression through NF-κB activation. .NO and lipid peroxidation occupied lysosomes as a major compartment with increased TFEB expression. Not only ferrostatin-1 but inhibitors for .NO and/or iNOS could suppress this ferroptosis. PAL-induced ferroptosis accompanied autophagic process in the early phase, as demonstrated by an increase in essential amino acids, LC3B-II, p62 and LAMP1, transforming into the later phase with boosted lipid peroxidation. Therefore, .NO-mediated lysosomal impairment is central in PAL-induced ferroptosis.

DOI： 10.1016/j.redox.2021.101989

Brain cell proliferation in adult rats after irradiation with nonequilibrium atmospheric pressure plasma 査読有り Open Access

Yamato, M; Tamura, Y; Tanaka, H; Ishikawa, K; Ikehara, Y; Hori, M; Kataoka, Y

APPLIED PHYSICS EXPRESS 14 巻 ( 6 ) 頁： 067002 2021年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Nonequilibrium atmospheric pressure plasma (NEAPP) has the potential for a wide range of medical applications, including wound healing, blood coagulation, and malignant cell apoptosis. However, its effect on the mammalian central nervous system remains unclear. We studied histological changes in the cerebral cortex of adult rats, following irradiation of the brain surface with NEAPP. NEAPP irradiation made three laminar tissue structures and induced high proliferation of brain-resident immature cells as well as bone marrow-derived cells. These observations indicate that NEAPP irradiation induced rearrangement of cellular and tissue organization, including cell proliferation in the central nervous system in vivo.

DOI： 10.35848/1882-0786/ac03c1

Hydrogen peroxide in lactate solutions irradiated by non-equilibrium atmospheric pressure plasma 査読有り

Liu, Y; Ishikawa, K; Miron, C; Hashizume, H; Tanaka, H; Hori, M

PLASMA SOURCES SCIENCE & TECHNOLOGY 30 巻 ( 4 ) 2021年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Sources Science and Technology

A mechanism of hydrogen peroxide (H2O2) generation in plasma-activated lactated Ringer's solution (PAL) has been analyzed. PAL was produced by irradiating a sodium lactate solution, a class of hydroxy acid, with non-equilibrium atmospheric pressure plasma (NEAPP). The concentration of H2O2 generation was dependent on the initial lactate concentrations, which ranged from 0-28 mM. However, the generation of H2O2 was inhibited by higher lactate concentration. The formation of H2O2 is proposed by catalyzed lactate and radicals in aqueous solution, such as OH, H and OO, during the plasma treatments.

DOI： 10.1088/1361-6595/abbbd4

Influences of substrate temperatures on etch rates of PECVD-SiN thin films with a CF4/H2 plasma 査読有り

Hsiao, SN; Nakane, K; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

APPLIED SURFACE SCIENCE 542 巻頁： 148550 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

The dependence of substrate temperatures (50 to −20 °C) on etch rate in two kinds of PECVD SiN films were investigated by a CF<inf>4</inf>/H<inf>2</inf> mixture plasma. The XRR and XPS results indicate that the chemical composition and film density were almost identical for the films. The FTIR shows that the ratio of N[sbnd]H and Si[sbnd]H groups were found to be significantly different in the SiN films. The N[sbnd]H rich films exhibited a lower etch rate at −20 °C than that observed at room temperature or higher, whereas the Si[sbnd]H rich films showed a higher etch rate at −20 °C. We found that the fluorocarbon thickness was thicker in the Si[sbnd]H rich samples than N[sbnd]H rich samples. The fact suggests that hydrogen originated from the broken Si[sbnd]H bonds enhanced the polymerization, which causes the decrease of etch rate. A thinner fluorocarbon thickness was found in the Si[sbnd]H rich samples at low temperature, which results in the higher etch rate. Angular-resolved XPS indicates that N[sbnd]H bonding formed easier on film surface at −20 °C. These results indicate that the bonding structure and substrate temperature affected the fluorocarbon thickness, fluorine reaction probability and hydrogen dissociation during the SiN etching.

DOI： 10.1016/j.apsusc.2020.148550

Selective etching of SiN against SiO2 and poly-Si films in hydrofluoroethane chemistry with a mixture of CH2FCHF2, O2, and Ar 査読有り

Hsiao, SN; Ishikawa, K; Hayashi, T; Ni, JW; Tsutsumi, T; Sekine, M; Hori, M

APPLIED SURFACE SCIENCE 541 巻頁： 148439 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Gas chemistry has a significant impact on etch selectivity in semiconductor device fabrication, which is important for realization of atomic-scale removal and formation of high-aspect ratio features. To widen the controllable changes in the etchant composition in etching processes, our previous calculation showed the possibility of the controllable generation of CH<inf>2</inf>F and CHF<inf>2</inf> related ions and radicals from a 1,1,2-trifluoroethane (CH<inf>2</inf>FCHF<inf>2</inf>) parent gas. The etch selectivity among silicon nitride (SiN), silicon dioxide (SiO<inf>2</inf>) and poly-Si films using CH<inf>2</inf>FCHF<inf>2</inf> plasma mixed with O<inf>2</inf> and Ar was investigated. The effects of the CH<inf>2</inf>FCHF<inf>2</inf> and O<inf>2</inf> partial pressures on the composition of CHF<inf>2</inf>+ and CH<inf>2</inf>F+ ions, which were measured with a quadrupole mass spectrometer, and on the possible reactions with respect to the CH<inf>2</inf>FCHF<inf>2</inf> and O<inf>2</inf> mixed gas phase were investigated using quantum chemical calculations. The etch selectivity was investigated through surface etching reactions for SiN, SiO<inf>2</inf>, and poly-Si films.

DOI： 10.1016/j.apsusc.2020.148439

酸素ラジカル処理肥料溶液を用いた殺菌でのピロール化合物の重要性査読有り

岩田直幸, 石川健治, 堀勝, 田中宏昌, 伊藤昌文, 橋爪博司

応用物理学会学術講演会講演予稿集 2021.1 巻 ( 0 ) 頁： 1554 - 1554 2021年2月

かいわれ大根種子の発芽と発芽の成長に対する大気圧プラズマ照射の影響－種子の色と貯蔵の効果査読有り

奥村賢直, 石川健治, 古閑一憲, 白谷正治, ヴィダミルダズィネ, アトリパンカジ

応用物理学会学術講演会講演予稿集 2021.1 巻 ( 0 ) 頁： 1514 - 1514 2021年2月

FOREWORD Mechanistic understanding of cold atmospheric plasma applications 査読有り Open Access

Kurihara, K; Ishikawa, K; Takaki, K; Shiratani, M

JAPANESE JOURNAL OF APPLIED PHYSICS 60 巻 ( 2 ) 2021年2月

Growth inhibition effect on Trypanosoma brucei gambiense by the oxidative stress supplied from low-temperature plasma at atmospheric pressure 査読有り Open Access

Yokoyama, N; Sivakumar, T; Ikehara, S; Akimoto, Y; Yamaguchi, T; Wakai, K; Ishikawa, K; Hori, M; Shimizu, T; Sakakita, H; Ikehara, Y

JAPANESE JOURNAL OF APPLIED PHYSICS 60 巻 ( 2 ) 頁： 020601 2021年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Trypanosoma brucei (Tb) is a pathogenic protozoan causing sleeping sickness in humans. Despite little knowledge of how the produced reactive oxygen species (ROS) kills this protozoan, the research on the killing mechanism using chemical compounds and the phagosome in the macrophages has suggested that the protozoan is highly susceptible to the increased oxidative stress. Because the prescribed drug can react with various kinds of molecules and the second produced intermediate compounds, in this study, we clarified the immediate killing effect on Tb in the condition of increased oxidative stress using a low-temperature plasma at atmospheric pressure (LTP) equipment. Results Show the significant growth inhibition of Tb in the LTP-treated medium, the loss of morphological homeostasis with twisted to puffed appearance, and demonstrated the swelled changes on mitochondria and endoplasmic reticulum. In conclusion, this study revealed how the increased oxidative stress kills Tb using LTP technology.

DOI： 10.35848/1347-4065/abd464

Insights into normothermic treatment with direct irradiation of atmospheric pressure plasma for biological applications 査読有り

Effects of Carbon Nanowalls (CNWs) Substrates on Soft Ionization of Low-Molecular-Weight Organic Compounds in Surface-Assisted Laser Desorption/Ionization Mass Spectrometry (SALDI-MS) 査読有り Open Access

Sakai, R; Ichikawa, T; Kondo, H; Ishikawa, K; Shimizu, N; Ohta, T; Hiramatsu, M; Hori, M

NANOMATERIALS 11 巻 ( 2 ) 頁： 1 - 11 2021年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nanomaterials

Carbon nanowalls (CNWs), which are vertically oriented multi-layer graphene sheets, were employed in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) measurements to detect low-molecular-weight organic compounds. CNWs substrates with widely different wall-to-wall distances from 142 to 467 nm were synthesized using a radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD) system with nanosecond pulse biasing to a sample stage. When survival yield (SY) values of N-benzylpyridinium chloride (N-BP-Cl) were examined, which is commonly used to evaluate desorption/ionization efficiency, a narrower wall-to-wall distance presented a higher SY value. The highest SY value of 0.97 was realized at 4 mJ/cm2 for the highest-density CNWs with a wall-to-wall distance of 142 nm. The laser desorption/ionization effect of arginine, an amino acid, was also investigated. When CNWs with a narrower wall-to-wall distance were used, the signal-to-noise (SN) ratios of the arginine signals were increased, while the intensity ratios of fragment ions to arginine signals were suppressed. Therefore, the CNWs nanostructures are a powerful tool when used as a SALDI substrate for the highly efficient desorption/ionization of low-molecular-weight biomolecules.

DOI： 10.3390/nano11020262

Impact of seed color and storage time on the radish seed germination and sprout growth in plasma agriculture 査読有り国際共著 Open Access

Attri, P; Ishikawa, K; Okumura, T; Koga, K; Shiratani, M; Mildaziene, V

SCIENTIFIC REPORTS 11 巻 ( 1 ) 頁： 2539 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

The use of low-temperature plasma for the pre-sowing seed treatment is still in the early stage of research; thus, numerous factors affecting germination percentage, seedling growth, and yield remains unknown. This study aimed to estimate how two critical factors, such as harvest year and seed coat color, affect the percentage of germination and seedling growth after plasma treatment. Radish seeds stored for 2 and 1 year after harvesting (harvested in 2017 and 2018) were sorted into two colors (brown and grey) to investigate the plasma effect on harvest year and seed coat color. We analyzed the amounts of seed phytohormones and antioxidant (γ-tocopherol) were analyzed using mass spectrometry, and physical changes were studied using SEM, EDX, and EPR to understand the mechanism of plasma-induced changes in radish seeds. The obtained results revealed that plasma treatment on seeds affects the germination kinetics, and the maximal germination percentage depends on seed color and the time of seed storage after harvest. Through this study, for the first time, we demonstrated that physical and chemical changes in radish seeds after plasma treatment depends upon the seed color and harvest year. Positive effects of plasma treatment on growth are stronger for sprouts from seeds harvested in 2017 than in 2018. The plasma treatment effect on the sprouts germinated from grey seeds effect was stronger than sprouts from brown radish seeds. The amounts of gibberellin A3 and abscisic acid in control seeds strongly depended on the seed color, and plasma induced changes were better in grey seeds harvested in 2017. Therefore, this study reveals that Air scalar-DBD plasma's reactive oxygen and nitrogen species (RONS) can efficiently accelerate germination and growth in older seeds.

DOI： 10.1038/s41598-021-81175-x

Yoshimura S., Otsubo Y., Yamashita A., Ishikawa K.

Japanese Journal of Applied Physics 60 巻 ( 1 ) 頁： 010502 2021年1月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Characterizing the interactions between plasma and living organisms has become a multidisciplinary topic in the field of low-temperature plasma science and technology. Living organisms are hierarchically comprised of cells, tissues, organs, and organ systems. Adaptive responses are systematically controlled by the state of the surrounding environment, such as when living organisms are irradiated with discharge plasma. This review is written from a biological perspective and focuses on the importance of gas temperature control in nonequilibrium atmospheric pressure plasmas. We discuss the critical parameters associated with direct plasma treatments of living organisms. This review provides an assessment of the status of this research field and addresses the prospects for further developments in understanding the interactions between plasma and living organisms. We address the importance and necessity of normothermic plasma treatment, where an experimental system involving living organisms is controlled at an optimal temperature, which plays a significant role in plasma biology.

DOI： 10.35848/1347-4065/abcbd2

Reduction in photon-induced interface defects by optimal pulse repetition rate in the pulse-modulated inductively coupled plasma 査読有り

Miyoshi Y., Ishikawa K., Sekine M., Hori M., Tatsumi T.

Japanese Journal of Applied Physics 60 巻 ( 1 ) 頁： 010906 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The ultraviolet photon-induced interface defects that degrade the performance of a semiconductor device are reduced by the optimal pulse repetition rate of a pulse-modulated inductively coupled plasma. The defect density depends on the pulse repetition rates; it takes minimum value at a few hundred pulses s−1 and peaks at a few k pulses s−1. The repetition rate-dependent behavior is suggested to be caused by the transient behavior between the plasma's ON and OFF phases. Note that controlling the transient behavior for reducing the photon-induced damage is essential.

DOI： 10.35848/1347-4065/abd113

Improvement of yield and grain quality by periodic cold plasma treatment with rice plants in a paddy field 査読有り

Hashizume, H; Kitano, H; Mizuno, H; Abe, A; Yuasa, G; Tohno, S; Tanaka, H; Ishikawa, K; Matsumoto, S; Sakakibara, H; Nikawa, S; Maeshima, M; Mizuno, M; Hori, M

PLASMA PROCESSES AND POLYMERS 18 巻 ( 1 ) 頁： 2000181 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

The application of cold plasma has attracted considerable attention in the field of agriculture. We examined the effects of plasma irradiation and treatment with plasma-activated Ringer's lactate solution (PAL) on rice seedlings in a paddy field. Irradiation during the vegetative growth period increased seedling growth, panicle number, and grain yield. In contrast, treatment during the reproductive growth period had a negative or no effect. Moreover, treatment with PAL solution promoted the growth of the main stem, such as grain number and panicle weight, and grain quality, but the grain yield from the whole plant was decreased. The results suggest that cold plasma treatment of rice seedlings is effective for improving plant growth, grain yield, and grain quality.

DOI： 10.1002/ppap.202000181

Cancer Treatments Using Low-Temperature Plasma 査読有り

Tanaka, H; Mizuno, M; Ishikawa, K; Toyokuni, S; Kajiyama, H; Kikkawa, F; Hori, M

CURRENT MEDICINAL CHEMISTRY 28 巻 ( 41 ) 頁： 8549 - 8558 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Current Medicinal Chemistry

Low-temperature plasma (LTP) is a partially ionized gas that contains elec-trons, ions, radicals, light, etc. Recently, the bio-medical application of LTP has become a hot topic in plasma science and biological science. Cancer treatment with plasma is the most challenging topic in plasma bio-medical applications. Many in vitro and in vivo ex-periments have been conducted to investigate the anti-tumor effects of LTP. Extracellular reactive oxygen and nitrogen species (RONS) in plasma-activated solutions are key factors for the anti-tumor effects, and amino acid modifications by LTP may affect cellular responses. Intracellular RONS are also key factors for the anti-tumor effects. Various signaling pathways, such as p53 signaling pathways, survival and proliferation signaling pathways, and oxidative stress-dependent signaling pathways are activated by LTP.

DOI： 10.2174/0929867328666210629121731

同軸型誘電体バリア放電におけるプラズマの形成過程の数値解析

Numerical analysis of high-electron-density atmospheric pressure argon streamer under a pin-to-plane electrode geometry: Effects of applying voltage polarity 査読有り Open Access

Sato Y., Ishikawa K., Tsutsumi T., Ui A., Akita M., Oka S., Hori M.

47th Eps Conference on Plasma Physics Eps 2021 2021-June 巻頁： 45 - 48 2021年

佐藤陽介, 宇井明生, 岡将太郎, 堤隆嘉, 石川健治, 森山達行, 堀勝

年次大会 2021 巻 ( 0 ) 頁： S053-01 2021年

Reaction science of layer-by-layer thinning of graphene with oxygen neutrals at room temperature 査読有り

Sugiura, H; Kondo, H; Higuchi, K; Arai, S; Hamaji, R; Tsutsumi, T; Ishikawa, K; Hori, M

CARBON 170 巻頁： 93 - 99 2020年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Carbon

Controlling the layers and in-plane defects in multi-layer graphene is the key to exploiting the extraordinary properties of graphene. Layer-by-layer thinning under high-density oxygen neutrals was observed in situ during room-temperature reaction science using a remote oxygen plasma inside a high-voltage transmission electron microscopy. Even though the etching rate of graphene was higher at the edge than at the basal plane, etching started from both locations. Each etched layer was represented by the plasmon loss intensity in the electron energy loss spectrum. After exposure to the remote oxygen plasma, the electron diffraction pattern for the multi-layer graphene keep clear six-fold diffraction pattern. Raman spectroscopy revealed the formation of defects in multi-layer graphene. The nonthermal reaction of oxygen neutrals required for graphene etching was demonstrated by in situ transmission electron microscopy.

DOI： 10.1016/j.carbon.2020.07.052

Influence of chamber pressure on the crystal quality of homo-epitaxial GaN grown by radical-enhanced MOCVD (REMOCVD) 査読有り

Amalraj, FW; Shimizu, N; Oda, O; Ishikawa, K; Hori, M

JOURNAL OF CRYSTAL GROWTH 549 巻頁： 125863 2020年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Crystal Growth

III-nitride was grown by radical-enhanced metalorganic chemical vapor deposition (REMOCVD) with a very high-frequency electric source 100 MHz, using nitrogen and hydrogen as a source gas free from ammonia gas. Applying radio frequency (RF) power at the top electrode generates activated nitrogen, hydrogen, and other nitrogen species. Homoepitaxial gallium nitride (GaN) growth was studied as a function of chamber pressure by REMOCVD. The grown GaN was characterized by scanning electron microscope (SEM), atomic force microscope (AFM), and double crystal X-ray diffraction (XRD). Ga radicals and N radicals were detected by optical emission spectroscopy (OES) as a function of chamber pressure. The V/III ratio changes with the N<inf>2</inf>*/Ga* ratio, and the step flow growth of GaN was achieved under the chamber pressure of 300 Pa.

DOI： 10.1016/j.jcrysgro.2020.125863

Steering of surface discharges on through-glass-vias combined with high-density nonequilibrium atmospheric pressure plasma generation 査読有り

Sato, Y; Katsuno, K; Odaka, H; Imajyo, N; Ishikawa, K; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 53 巻 ( 43 ) 頁： 534302 2020年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

The concept of using a glass substrate with fine through-holes filled with metal, called through-glass-vias (TGVs), for an inner wall of an enclosure of a nonequilibrium atmospheric pressure plasma source was validated to extend its processing area with high plasma densities maintained. When applying the TGV substrate into an inner wall of the plasma source, the generated discharge was less likely to drift along with the gas flow, which resembled the behavior of locally high electric fields of the plasma source, called the creeping mode. The decrease in breakdown voltage was also observed. These phenomena are caused by the TGV areas acting as a steering control material in the enclosure of the plasma source. The location of the TGV areas affected the behavior of the generated plasma. The shape of the plasma was accomplished to arbitrarily and locally control by the placement of TGVs.

DOI： 10.1088/1361-6463/aba1ad

Formation of spherical Sn particles by reducing SnO2 film in floating wire-assisted H2/Ar plasma at atmospheric pressure 査読有り Open Access

Nguyen, TTN; Sasaki, M; Tsutsumi, T; Ishikawa, K; Hori, M

SCIENTIFIC REPORTS 10 巻 ( 1 ) 頁： 17770 2020年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

A green method to synthesize spherical Sn particles by reducing SnO<inf>2</inf> film in atmospheric-pressure H<inf>2</inf>/Ar plasma at low temperatures for various applications is presented. The floating wire-assisted remotely-generated plasma with a mixture of 0.05% H<inf>2</inf>/Ar gas formed spherical metallic Sn particles by reducing a SnO<inf>2</inf> layer on glass substrate. During the reduction process, H radical density was measured by using vacuum ultraviolet absorption spectroscopy, and plasma properties including electron density and gas temperature were diagnosed by optical emission spectroscopy. The inductively coupled generated plasma with a high electron density of 1014 cm−3, a hydrogen atom density of 1014 cm−3, and a gas temperature of 940 K was obtained at a remote region distance of 150 mm where the SnO<inf>2</inf>/glass substrate was placed for plasma treatment. The process has been modeled on the spherical Sn formation based on the reduction of SnO<inf>2</inf> films using H radicals. Depending on the treatment condition, the total reduction area, where spherical Sn particles formed, was enlarged and could reach 300 mm2 after 2 min. The substrate temperature affected the expansion rate of the total reduction area and the growth of the Sn spheres.

DOI： 10.1038/s41598-020-74663-z

Roles of Atomic Nitrogen/Hydrogen in GaN Film Growth by Chemically Assisted Sputtering with Dual Plasma Sources 査読有り Open Access

Tanide, A; Nakamura, S; Horikoshi, A; Takatsuji, S; Kimura, T; Kinose, K; Nadahara, S; Nishikawa, M; Ebe, A; Ishikawa, K; Oda, O; Hori, M

ACS OMEGA 5 巻 ( 41 ) 頁： 26776 - 26785 2020年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Omega

The growth of sputtered GaN at low temperature is strongly desired to realize the dissemination of low-cost GaN high electron mobility transistor devices for next-generation communication technology. In this work, the roles of atomic nitrogen (N)/hydrogen (H) in GaN film growth on AlN/sapphire substrates by chemically assisted dual source sputtering are studied at a low growth temperature of 600 °C under a pressure of 2 Pa using vacuum ultraviolet absorption spectroscopy. The lateral growth was strongly enhanced with an appropriate H/N flux ratio of 1.9 at a GaN growth rate of ∼1 μm h-1. X-ray photoelectron spectroscopy measurements indicated that N removal from the grown GaN surface by atomic hydrogen promoted the migration of Ga. A smooth GaN surface was achieved at a suitable N/Ga supply ratio of 53 and a H/N ratio of 1.9 with the addition of 0.5% chlorine to the Ar sputtering gas.

DOI： 10.1021/acsomega.0c03865

Laser-induced-plasma-activated medium enables killing of HeLa cells 査読有り

Kurokawa Y., Takeda K., Ishikawa K., Tanaka H., Hori M.

Applied Physics Express 13 巻 ( 10 ) 2020年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Plasma-activated medium (PAM) is defined as a medium irradiated with non-thermal plasma; multiple in vitro and animal experiments have demonstrated that PAM exhibits anti-tumor effects against various cancers. PAM contains various reactive species that contribute to these anti-tumor effects. To increase the abundance of such reactive species, we used laser-generated plasma (LGP). We used a LGP consisting of 200 ns pulsed plasma with an electron density of approximately 7.0 × 1018 cm−3, which is an extremely high electron density, exceeding those of other atmospheric pressure plasmas. We created a laser-generated-plasma-activated medium (LPAM), and treated HeLa cells with the LPAM in both the presence and absence of catalase. Both with and without catalase, the LPAM treatment yielded strong anti-cancer effects against HeLa cells. Surprisingly, we observed morphological differences between HeLa cells grown in LPAM prepared with and without catalase. These results suggested that LPAM induces the cell death through extracellular hydrogen peroxide-dependent and -independent processes.

DOI： 10.35848/1882-0786/abb68c

Adjusted multiple gases in the plasma flow induce differential antitumor potentials of plasma-activated solutions 査読有り

Nakamura, K; Yoshikawa, N; Yoshihara, M; Ikeda, Y; Higashida, A; Niwa, A; Jindo, T; Tanaka, H; Ishikawa, K; Mizuno, M; Toyokuni, S; Hori, M; Kikkawa, F; Kajiyama, H

PLASMA PROCESSES AND POLYMERS 17 巻 ( 10 ) 頁： 1900259 2020年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

We present a novel plasma system that can generate a plasma-activated medium by changing the proportion of reactive gases such as oxygen, nitrogen, and hydrogen in the plasma flow. The correlation between the biological activity of plasma-activated solutions prepared under multiple plasma gas-flow conditions was evaluated. Mixed nitrogen, in addition to oxygen, in the gas flow is most powerful for producing plasma-activated Ringer's lactate solution against antitumor effects on ovarian cancer cells as compared with oxygen or nitrogen alone. The antitumor effect of plasma-activated solutions is controllable by the modification of the proportion of reactive gases (especially nitrogen and oxygen gases) in the plasma flow. These results suggest that the plasma flow conditions may be one of the candidates for the specifications of the plasma-activated solutions to the therapeutic effect.

DOI： 10.1002/ppap.201900259

Small size gold nanoparticles enhance apoptosis-induced by cold atmospheric plasma via depletion of intracellular GSH and modification of oxidative stress 査読有り Open Access

Jawaid, P; Rehman, MU; Zhao, QL; Misawa, M; Ishikawa, K; Hori, M; Shimizu, T; Saitoh, J; Noguchi, K; Kondo, T

CELL DEATH DISCOVERY 6 巻 ( 1 ) 頁： 83 2020年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Cell Death Discovery

Gold nanoparticles (Au-NPs) have attracted attention as a promising sensitizer owing to their high atomic number (Z), and because they are considered fully multifunctional, they are preferred over other metal nanoparticles. Cold atmospheric plasma (CAP) has also recently gained attention, especially for cancer treatment, by inducing apoptosis through the formation of reactive oxygen species (ROS). In this study, the activity of different sized Au-NPs with helium-based CAP (He-CAP) was analyzed, and the underlying mechanism was investigated. Treating cells with only small Au-NPs (2 nm) significantly enhanced He-CAP-induced apoptosis. In comparison, 40 nm and 100 nm Au-NPs failed to enhance cell death. Mechanistically, the synergistic enhancement was due to 2 nm Au-NPs-induced decrease in intracellular glutathione, which led to the generation of intracellular ROS. He-CAP markedly induced ROS generation in an aqueous medium; however, treatment with He-CAP alone did not induce intracellular ROS formation. In contrast, the combined treatment significantly enhanced the intracellular formation of superoxide (O<inf>2</inf>• −) and hydroxyl radical (•OH). These findings indicate the potential therapeutic use of Au-NPs in combination with CAP and further clarify the role of Au-NPs in He-CAP-aided therapies.

DOI： 10.1038/s41420-020-00314-x

酒米品種イネ栽培における低温プラズマ処理の品質への効果査読有り

水野寛子, 橋爪博司, 北野英己, 阿部明子, 湯浅元気, 堀勝, 東野里江, 榊原均, 松本省吾, 水野正明, 田中宏昌, 石川健治, 仁川進, 前島正義

応用物理学会学術講演会講演予稿集 2020.2 巻 ( 0 ) 頁： 1167 - 1167 2020年8月

Influence of temperature on etch rate of PECVD-SiN films with CF4/H2 plasma 査読有り

Hsiao Shihnan, Nakane Kazuya, Ishikawa Kenji, Tsutsumi Takayoshi, Hori Masaru, Sekine Makoto

JSAP Annual Meetings Extended Abstracts 2020.2 巻 ( 0 ) 頁： 1195 - 1195 2020年8月

Numerical analysis of coaxial dielectric barrier helium discharges: three-stage mode transitions and internal bullet propagation 査読有り Open Access

Sato, Y; Ishikawa, K; Tsutsumi, T; Hori, M

APPLIED PHYSICS EXPRESS 13 巻 ( 8 ) 頁： 086001 2020年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

He discharge in a coaxial dielectric barrier discharge (DBD) device develops in three stages: first, a Townsend-glow-type plasma spreads in the region between the electrodes; second, a plasma bullet (streamer type discharge) propagates axially and; third, the bullet transitions into a surface discharge at the dielectric surface. These mode transitions are quite different from planar type DBD, in which one discharge mode basically corresponds to one discharge pulse. From fluid-based numerical analysis, the bullet propagation is obeyed by trapping with strong electric fields induced by grounded electrode underneath the dielectric barrier and by surface charge accumulated on the dielectric surface.

DOI： 10.35848/1882-0786/aba3f2

Plasma Agriculture from Laboratory to Farm: A Review 査読有り Open Access

Attri, P; Ishikawa, K; Okumura, T; Koga, K; Shiratani, M

PROCESSES 8 巻 ( 8 ) 頁： 1002 2020年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Processes

In recent years, non-thermal plasma (NTP) application in agriculture is rapidly increasing. Many published articles and reviews in the literature are focus on the post-harvest use of plasma in agriculture. However, the pre-harvest application of plasma still in its early stage. Therefore, in this review, we covered the effect of NTP and plasma-treated water (PTW) on seed germination and growth enhancement. Further, we will discuss the change in biochemical analysis, e.g., the variation in phytohormones, phytochemicals, and antioxidant levels of seeds after treatment with NTP and PTW. Lastly, we will address the possibility of using plasma in the actual agriculture field and prospects of this technology.

DOI： 10.3390/pr8081002

Non-thermal plasma-activated lactate solution kills U251SP glioblastoma cells in an innate reductive manner with altered metabolism 査読有り

Ishikawa, K; Hosoi, Y; Tanaka, H; Jiang, L; Toyokuni, S; Nakamura, K; Kajiyama, H; Kikkawa, F; Mizuno, M; Hori, M

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS 688 巻頁： 108414 2020年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Archives of Biochemistry and Biophysics

Ringer's lactate solution irradiated by non-thermal plasma, comprised of radicals, electrons, and ions, is defined as plasma-activated lactate (PAL). PAL exhibited antitumor effects in glioblastoma U251SP cells, which we termed PAL-specific regulated cell death. In contrast to the oxidative stress condition typical of cells incubated in plasma-activated medium (PAM), U251SP cells treated with Ringer's lactate solution or PAL exhibited changes in intracellular metabolites that were reductive in the redox state, as measured by the ratio of oxidative/reductive glutathione concentrations. In the metabolomic profiles of PAL-treated cells, the generation of acetyl-CoA increased for lipid metabolism from alanine and asparagine. PAL thus induces regulated death of U251SP glioblastoma cells in more innate microenvironments than PAM.

DOI： 10.1016/j.abb.2020.108414

In situ surface analysis of an ion-energy-dependent chlorination layer on GaN during cyclic etching using Ar+ ions and Cl radicals 査読有り

Hasegawa, M; Tsutsumi, T; Tanide, A; Nakamura, S; Kondo, H; Ishikawa, K; Sekine, M; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 38 巻 ( 4 ) 頁： 042602 2020年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology A Vacuum Surfaces and Films

Gallium nitride (GaN) semiconductor devices must be fabricated using plasma etching with precise control of the etching depths and minimal plasma-induced damage on the atomic scale. A cyclic process comprising etchant adsorption and product removal may be suitable for this purpose but an understanding of the associated etching surface reactions is required. The present work examined the formation of a chlorinated layer based on Cl radical adsorption on a GaN surface in conjunction with Ar ion irradiation. This research employed beam experiments and in situ x-ray photoelectron spectroscopy. The results show that N atoms are preferentially desorbed during exposure to Ar ions to produce Ga-rich layers at depths of 0.8 and 1.1 nm at an Ar ion dosage on the order of 1016 cm-2 and ion energies of 116.0 and 212.6 eV, respectively. Subsequent exposure of the irradiated Ga-rich layer to Cl radicals removes some Ga atoms and produces a chlorinated layer over the GaN surface. This chlorinated layer has a thickness on the order of 1 nm following Cl radical dosages on the order of 1019 cm-2. This study of plasma-treated surfaces is expected to assist in developing means of controlling the etching depth during the atomic layer etching of GaN via Ar ion bombardment.

DOI： 10.1116/6.0000124

Numerical simulations of stable, high-electron-density atmospheric pressure argon plasma under pin-to-plane electrode geometry: effects of applied voltage polarity 査読有り Open Access

Sato, Y; Ishikawa, K; Tsutsumi, T; Ui, A; Akita, M; Oka, S; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 53 巻 ( 26 ) 頁： 265204 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

When applying high-voltage direct current to a pin-to-plane electrode geometry with a distance of 2 mm under atmospheric pressure in argon gas, electrical breakdown forms primary then secondary streamers. The polarity of the applied voltage affects this streamer-propagating phenomenon. Properties such as propagation speed, streamer head size, and plasma generation are parameterized at nanosecond scales by computational simulations of a self-consistent, multi-species, multierature plasma fluid modeling approach. For positive polarity on the pin electrode, streamer-head propagation speeds up and streamer head size increases with increasing applied voltages. However, local electron density at the head decreases. For negative polarity, corona-like discharges form around the pin electrode under low applied voltages, and diffusive steamers form under high applied voltages. Secondary streamers re-propagate from the pin after primary streamer propagation, forming a plasma with a high electron density of 1021 m-3 for the positive polarity. We show that low-voltage operations with positive polarity are useful for stable high-electron-density discharges under atmospheric pressure argon.

DOI： 10.1088/1361-6463/ab7df0

In-plane modification of hexagonal boron nitride particles via plasma in solution 査読有り Open Access

Ito, T; Goto, T; Inoue, K; Ishikawa, K; Kondo, H; Hori, M; Shimizu, Y; Hakuta, Y; Terashima, K

APPLIED PHYSICS EXPRESS 13 巻 ( 6 ) 頁： 066001 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

In-plane modification of hexagonal boron nitride (hBN) is demonstrated via plasma in solution without acid/base addition. Electron spin resonance spectroscopy clearly reveals an increase in nitrogen vacancies in the hBN plane. This could be a simple route to functionalizing the two-dimensional surface of hBN. Simultaneously, hydroxylation occurs, accompanied by an increase in the zeta potential.

DOI： 10.35848/1882-0786/ab916c

Characterization of a microsecond pulsed non-equilibrium atmospheric pressure Ar plasma using laser scattering and optical emission spectroscopy 査読有り

Dry Process FOREWORD 査読有り

Shirafuji, T; Kinoshita, K; Akatsuka, H; Eriguchi, K; Ichikawa, T; Ichiki, T; Ishijima, T; Ishikawa, K; Karahashi, K; Kurihara, K; Sekine, M

JAPANESE JOURNAL OF APPLIED PHYSICS 59 巻 ( SJ ) 2020年6月

Jia, FD; Wu, Y; Min, Q; Su, MG; Takeda, K; Ishikawa, K; Kondo, H; Sekine, M; Hori, M; Zhong, ZP

PLASMA SCIENCE & TECHNOLOGY 22 巻 ( 6 ) 頁： 065404 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Science and Technology

A non-equilibrium atmospheric pressure argon (Ar) plasma excited by microsecond pulse is studied experimentally by laser scattering and optical emission spectroscopy (OES), and theoretically by collisional-radiative (CR) model. More specifically, the electron temperature and electron density of plasma are obtained directly by the laser Thomson scattering, the gas temperature is measured by laser Raman scattering, the optical emissions of excited Ar states of plasma are measured by OES. The laser scattering results show that the electron temperature is about 1 eV which is similar to that excited by 60 Hz AC power, but the gas temperature is as low as 300 K compared to about 700 K excited by 60 Hz AC power. It is shown that the microsecond pulsed power supply, rather than nanosecond ones, is short enough to reduce the gas temperature of atmospheric pressure plasma to near room temperature. The electron temperature and electron density are also obtained by CR model based on OES, and find that the intensities of the optical emission intensity lines of 727.41, 811.73, 841.08, 842.83, 852.44 and 912.86 nm of Ar can be used to characterize the behavior of electron density and electron temperature, it is very useful to quickly estimate the activity of the atmospheric pressure Ar plasma in many applications.

DOI： 10.1088/2058-6272/ab84e2

Electron spin resonance as a tool to monitor the influence of novel processing technologies on food properties 査読有り国際共著 Open Access

Barba, FJ; Roohinejad, S; Ishikawa, K; Leong, SY; Bekhit, AEA; Saraiva, JA; Lebovka, N

TRENDS IN FOOD SCIENCE & TECHNOLOGY 100 巻頁： 77 - 87 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Trends in Food Science and Technology

Background: Nowadays, electron spin resonance (ESR) is widely used as a powerful, non-destructive and very sensitive technique for the detection of free radicals in food systems. It can be applied for the direct identification of highly reactive oxygen species, organic and inorganic paramagnetic species and screening of food for potential toxicity. Its applications cover investigating food oxidative stability and properties of irradiated foods including fruits and vegetables, meats and fishes, spices, cereal grains, and oil seeds. Scope and approach: This review aims at providing specialists in food science and industry with the fundamentals of ESR spectroscopy, typical radicals present in foods and their sources, ESR modalities, and detailed account for the use of the technology for evaluation of the physicochemical and nutritional properties of foods. Examples illustrating ESR applications for the evaluation of the effects of innovative and emerging technologies (ionizing radiation, high pressures, pulsed electric fields, cold plasma and ultrasonication) are discussed. Key findings and conclusions: ESR can be used for the identification/quantification of free radicals in foods, for spin-label oximetry, estimation of free radical scavenging, food stability, and chelating activity, with particular interest for food processed using innovative technologies, with the main advantages of its high sensitivity, specificity, and low amounts of sample needed and nowadays many types of ESR instruments are commercially available. However, due to the different nature of foods, the development of novel ESR techniques and methods of analysis specially designed to study foods is of great interest in the future.

DOI： 10.1016/j.tifs.2020.03.032

Electronic properties and primary dissociation channels of fluoromethane compounds 査読有り

Hayashi, T; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 59 巻 ( SJ ) 頁： SJJE02 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

We investigated fluoromethane compounds (CF<inf>4</inf>, CF<inf>3</inf>, CHF<inf>3</inf>, CH<inf>2</inf>F<inf>2</inf>, and CH<inf>3</inf>F) to examine their electronic properties and primary dissociation channels by using computational chemistry. For the electron attachment process, it was very important to represent the observed negative mass spectrum as a function of electron energy that calculation by the MP2 method for the negative ion and subsequent calculation by the EOMCCSD method were used to more accurately estimate the ground and the first excited states of the negative ion. In the evaluation of dissociation channels through the excitation process, the structure change of the excited fragment (from pyramidal to planar) was taken into account. Evaluation of Jahn-Teller distortion for the highly symmetrical CHF<inf>3</inf> and CH<inf>3</inf>F was also very important to estimate the fragmentation process through the excitation. The calculated results after these treatments gave satisfactory representation of the experimental values. Moreover some predictions of experimentally unknown values are proposed.

DOI： 10.35848/1347-4065/ab7e3f

Synthesis of isolated carbon nanowalls via high-voltage nanosecond pulses in conjunction with CH4/H2 plasma enhanced chemical vapor deposition 査読有り

Ichikawa, T; Shimizu, N; Ishikawa, K; Hiramatsu, M; Hori, M

CARBON 161 巻頁： 403 - 412 2020年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Carbon

Carbon nanowalls (CNWs) are vertically standing, interconnecting flake- or wall-like collections of graphene sheets. In the present work, this material was synthesized by applying precisely controlled high-voltage nanosecond pulses to a substrate using an inductor energy storage circuit in a radical-injection plasma-enhanced chemical vapor deposition system, employing a CH<inf>4</inf>/H<inf>2</inf> plasma. The resulting interconnected networks had a low density of CNWs with large average wall-to-wall distances. During the application of short-period pulses, the entire substrate surface was uniformly activated, thus enhancing the adsorption of carbon precursors and preventing CNW nucleation. As a result, an amorphous carbon film covered the surface of the substrate and a low CNW density was obtained with average wall-to-wall distances greater than 700 nm. On the basis of these results, the growth mechanism of CNWs was modeled.

DOI： 10.1016/j.carbon.2020.01.064

Gas-phase and film analysis of hydrogenated amorphous carbon films: Effect of ion bombardment energy flux on sp2 carbon structures 査読有り

Sugiura, H; Ohashi, Y; Ishikawa, K; Kondo, H; Kato, T; Kaneko, T; Takeda, K; Tsutsumi, T; Hayashi, T; Sekine, M; Hori, M

DIAMOND AND RELATED MATERIALS 104 巻 2020年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Diamond and Related Materials

Hydrogenated amorphous carbon (a-C:H) films comprise nanoclustering graphites (nc-G), fused aromatic rings (nR), and olefinic chain clusters (nC) of sp2-bonded carbons in an sp3 matrix. In this study, the sp2 composition of the nc-G, nR and nC in a-C:H films is found to be determined by the ion bombardment energy flux (Γ<inf>Ei</inf>), which can be estimated as the product of ion bombardment energy and ion flux onto the deposited surface, in plasma-enhanced chemical vapor deposition using a plasma mixture of H<inf>2</inf> and CH<inf>4</inf> gases with the H radical injection method. The sp2 composition is analyzed using Raman spectroscopy and near-edge X-ray absorption structure spectroscopy. a-C:H becomes increasingly graphitized with increasing Γ<inf>Ei</inf>. The precise control of the sp2 C structure composition can be achieved by controlling the very-high-frequency input power and radio frequency input bias power via the ion flux and ion bombardment energy.

DOI： 10.1016/j.diamond.2019.107651

In-Liquid Plasma Synthesis of Nanographene with a Mixture of Methanol and 1-Butanol 査読有り

Ando, A; Ishikawa, K; Takeda, K; Ohta, T; Ito, M; Hiramatsu, M; Kondo, H; Sekine, M; Hori, M

CHEMNANOMAT 6 巻 ( 4 ) 頁： 604 - 609 2020年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemnanomat

Nanometer-size graphene sheets (nanographene) were synthesized by the in-liquid plasma method employing a mixture of alcohols. Pure methanol in-liquid plasma was found to not synthesize any nanographene. Pure ethanol synthesized nanographene with high crystallinity. Highly crystalline nanographene with a narrow full width-half maximum of the Raman scattering G-band (FWHM<inf>G</inf>) was obtained by mixing 1-butanol with methanol. This is due to the formation of carbon ring structures being inhibited by the addition of methanol. The ratio of added methanol determined the nanographene crystallinity and yield under a trade-off relationship, allowing the crystallinity and nanographene yield to be controlled by controlling the ratio. Gas chromatography-mass spectrometric analysis of by-products in the liquids’ supernatant showed that the crystallinity of the synthesized nanographene correlated with the ratio of carbon over oxygen of the alcohol precursors (C/O), i. e., the amount of hydroxyl groups in the liquids, and hence controlling the C/O ratio can be used to control the graphene crystallinity in the in-liquid plasma synthesis.

DOI： 10.1002/cnma.201900676

計算科学による新規エッチングガスの探索査読有り

林俊雄, 関根誠, 堀勝, 石川健治

応用物理学会学術講演会講演予稿集 2020.1 巻 ( 0 ) 頁： 1585 - 1585 2020年2月

プラズマ照射したカイワレ種子の吸水の時間推移評価査読有り

石川健治, Pankaj Attri, 奥村賢直, 古閑一憲, 有田涼, 佐藤僚哉, 田中颯, 廣松真弥, 鎌瀧晋礼, 松尾かよ, 山下大輔, 板垣奈穂, 堀勝, 白谷正治

応用物理学会学術講演会講演予稿集 2020.1 巻 ( 0 ) 頁： 1620 - 1620 2020年2月

イネ圃場における定期的な低温プラズマ処理による生育や収穫に対する検討 (III) 査読有り

北野英己, 水野寛子, 阿部明子, 湯浅元気, 東野里江, 橋爪博司, 石川健治, 田中宏昌, 松本省吾, 仁川進, 榊原均, 前島正義, 堀勝, 水野正明

応用物理学会学術講演会講演予稿集 2020.1 巻 ( 0 ) 頁： 1622 - 1622 2020年2月

Interaction of oxygen with polystyrene and polyethylene polymer films: A mechanistic study 査読有り国際共著

Fukunaga, Y; Longo, RC; Ventzek, PLG; Lane, B; Ranjan, A; Hwang, GS; Hartmann, G; Tsutsumi, T; Ishikawa, K; Kondo, H; Sekine, M; Hori, M

JOURNAL OF APPLIED PHYSICS 127 巻 ( 2 ) 2020年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

In this work, first principles calculations combined with advanced surface diagnostics are used to unravel the mechanisms of plasma oxygen interaction with organic films of interest for advanced patterning in semiconductor device manufacturing. Results from a combination of x-ray photoelectron spectroscopy (XPS) diagnosed oxygen plasma exposed polystyrene films and first principles modeling of organic films (polystyrene, polyethylene, and derivatives) provide insights into how organic films are oxidized by oxygen atoms. XPS measurements show the rapid formation of C-O structures and their saturation after oxygen exposure on both pristine and argon bombarded polystyrene samples. Quantum mechanics calculations confirm that C-OH formation can be immediate without recourse to previously formed dangling bonds. Multiple oxygen impacts are required for scission of pristine ethylene carbon strands. Therefore, ethylene films can be converted to polyols that are stable, whereas more likely strands are broken before polyol formation through the formation of water and C=O. On the contrary, intermediate compounds with adjacent C=O bonds are not likely to form stable structures. The combination of XPS measurements and modeling implies that the oxidation of polystyrene and polyethylene is self-limiting on both hydrogen saturated and dehydrogenated (after argon ion plasma bombardment) surfaces.

DOI： 10.1063/1.5127863

Inactivation mechanism of fungal spores through oxygen radicals in atmospheric-pressure plasma 査読有り

Ito M., Hashizume H., Oh J.S., Ishikawa K., Ohta T., Hori M.

Japanese Journal of Applied Physics 60 巻 ( 1 ) 頁： 010503 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

A brief history of the development of our plasma technology for the disinfection of agricultural harvests is presented in this review. We focused on the influence of reactive oxygen species (ROS), e.g. ground-state oxygen atoms [O(3P j )], excited-state oxygen molecules [O2(1Δg)], and ozone (O3), generated from atmospheric-pressure plasmas on the inactivation of fungal spores under dry conditions. For elucidating the inactivation mechanisms, it is essential to reveal the key ROS. Using some powerful tools, we revealed that the dose of O(3P j ) strongly correlates with the inactivation of fungal spores when compared to those of another ROS, such as O2(1Δg) and O3. The balance of antioxidants in the spores is possibly modulated by O(3P j ), leading to oxidation of organelles in spores. Herein, we introduce and discuss how O(3P j ) contributes to the inactivation of fungal spores associated with in situ diagnostics of plasma generated ROS and in situ intracellular observations of a few fungal spore species.

DOI： 10.35848/1347-4065/abcbd1

Leukocyte depletion and size-based enrichment of circulating tumor cells with pressure-sensing microfiltration system 査読有り Open Access

Kuboyama D., Onoshima D., Kihara N., Tanaka H., Hase T., Yukawa H., Ishikawa K., Odaka H., Hasegawa Y., Hori M., Baba Y.

21st International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2017 頁： 882 - 883 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：21st International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2017

We present a study of blood microfiltration system towards optimal approach of non-invasive liquid biopsy for cancer detection by circulating tumor cells (CTCs). Filtration behavior of a microfilter was experimentally analyzed for tumor cell isolation from leukocytes in whole blood. This approach achieved an average of >96% recovery of spiked tumor cells and >99% total leukocytes depletion.

DOI： 10.1021/acsmeasuresciau.2c00057

Cell deposition and isolation with micropipette control over liquid interface motion in microfluidic channel 査読有り

Onoshima D., Yukawa H., Hattori Y., Ishikawa K., Hori M., Baba Y.

21st International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2017 頁： 679 - 680 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：21st International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2017

We developed a microfluidic chip for depositing single cells in microwells using simple micropipette operation. Cells were delivered to microwells by the meniscus motion of liquid interface. The residue deposits of cells were redistributed with air injection, and the isolated single cells were stored in microwells. Different microwell sizes and depths were studied to evaluate the trapping possibility of cells. Medium replacement and cell viability staining with the isolated single cells were achieved in microwells.

Etching characteristics of PECVD-prepared SiN films with CF4/D2 and CF4/H2 plasmas at different temperatures 査読有り

Hsiao, SN; Nguyen, TTN; Tsutsumi, T; Ishikawa, K; Sekine, M; Hori, M

2020 INTERNATIONAL SYMPOSIUM ON SEMICONDUCTOR MANUFACTURING (ISSM) 2020-December 巻 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings

The dependences of plasmas (CF4/D2 and CF4/H2) on etch rates of the PECVD SiN films at different substrate temperatures were investigated. The CF4/D2 plasma exhibited higher etch rates than that for the CF4/D2 plasma at room temperature and higher. The optical emission spectra showed that the CF polymerization, F and Balmer emissions were stronger in the CF4/D2 plasma, by comparing with the CF4/H2 plasma. A thinner fluorocarbon thickness with a lower F/C ratio was found in the sample proceeded by the CF4/H2 plasma. The fluorocarbon thickness and gas phase concentration were not responsible for the increase of etch rate in the CF4/D2 plasma. The abstraction of H inside the SiN films by deuterium and hydrogen dissociation were considered to be important for the etching of the Si-H bond rich SiN films.

DOI： 10.1109/ISSM51728.2020.9377537

無潤滑下及びベース油中におけるta-CNxコーティングのトライボロジー特性に及ぼすダングリングボンドと表面エネルギーの影響

宮地孝明, 中島悠也, 石川健治, Wooyoung Lee, 野老山貴行, 村島基之, 梅原徳次

年次大会 2020 巻 ( 0 ) 頁： S11314 2020年

Rapid thermal-cyclic atomic-layer etching of titanium nitride in CHF3/O2 downstream plasma 査読有り

Shinoda, K; Miyoshi, N; Kobayashi, H; Izawa, M; Ishikawa, K; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 52 巻 ( 47 ) 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

Isotropic atomic-layer etching (ALE) of TiN-by using a plasma-assisted thermal-cyclic process with a 300-mm tool-was demonstrated. The process consists of exposure to a downstream CHF<inf>3</inf>/O<inf>2</inf> plasma (for surface modification) followed by infrared irradiation for thermal desorption of the modified surface. Etched amount of TiN per cycle saturated at around 0.6 nm/cycle with respect to both radical-exposure time and infrared-irradiation time. To examine the reaction mechanism of the cyclic etching, the surfaces of TiN samples after CHF<inf>3</inf>/O<inf>2</inf> plasma exposure were analyzed by in situ X-ray photoelectron spectroscopy (XPS). Self-limiting formation of the surface-modified layer, which was tentatively identified as an ammonium salt such as (NH<inf>4</inf>)<inf>x</inf>TiF<inf>y</inf>, was observed after radical exposure. It was confirmed by in situ XPS that the surface-modified layer was removed after thermal annealing at 110 °C. Isotropic ALE of TiN was thus demonstrated by using formation and desorption of ammonium salt in CHF<inf>3</inf>/O<inf>2</inf> downstream plasma, which was also used for isotropic ALE of Si<inf>3</inf>N<inf>4</inf>.

DOI： 10.1088/1361-6463/ab3cf3

Simulation-aided design of very-high-frequency excited nitrogen plasma confinement using a shield plate 査読有り

Isobe, Y; Sakai, T; Suguro, K; Miyashita, N; Kondo, H; Ishikawa, K; Wilson, AF; Shimizu, N; Oda, O; Sekine, M; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 37 巻 ( 6 ) 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B Nanotechnology and Microelectronics

Nitrogen atoms are versatile for nitridation applications and do not lead to plasma-induced damage. Large-sized wafer processing demands a uniform supply of nitrogen atoms produced in a high-density very-high-frequency excited plasma of N<inf>2</inf> without ammonia. The confinement of plasma through the use of a plasma shield plate (PSP) allows the samples to be separated in a downstream chamber. Generation and transport of N atoms were computationally simulated, and the PSP designs were implemented by PSP parameterization. The supply of high-density N radicals to the sample stage was optimally designed with sufficiently small holes and thin PSP to satisfy an aspect ratio of thickness-to-hole-diameter of less than 2.5.

DOI： 10.1116/1.5114831

Review of methods for the mitigation of plasma-induced damage to low-dielectric-constant interlayer dielectrics used for semiconductor logic device interconnects 査読有り

Oxidative stress-dependent and -independent death of glioblastoma cells induced by non-thermal plasma-exposed solutions 査読有り Open Access

Tanaka, H; Mizuno, M; Katsumata, Y; Ishikawa, K; Kondo, H; Hashizume, H; Okazaki, Y; Toyokuni, S; Nakamura, K; Yoshikawa, N; Kajiyama, H; Kikkawa, F; Hori, M

SCIENTIFIC REPORTS 9 巻 ( 1 ) 頁： 13657 2019年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Non-thermal atmospheric pressure plasma has been widely used for preclinical studies in areas such as wound healing, blood coagulation, and cancer therapy. We previously developed plasma-activated medium (PAM) and plasma-activated Ringer’s lactate solutions (PAL) for cancer treatments. Many in vitro and in vivo experiments demonstrated that both PAM and PAL exhibit anti-tumor effects in several types of cancer cells such as ovarian, gastric, and pancreatic cancer cells as well as glioblastoma cells. However, interestingly, PAM induces more intracellular reactive oxygen species in glioblastoma cells than PAL. To investigate the differences in intracellular molecular mechanisms of the effects of PAM and PAL in glioblastoma cells, we measured gene expression levels of antioxidant genes such as CAT, SOD2, and GPX1. Microarray and quantitative real-time PCR analyses revealed that PAM elevated stress-inducible genes that induce apoptosis such as GADD45α signaling molecules. PAL suppressed genes downstream of the survival and proliferation signaling network such as YAP/TEAD signaling molecules. These data reveal that PAM and PAL induce apoptosis in glioblastoma cells by different intracellular molecular mechanisms.

DOI： 10.1038/s41598-019-50136-w

プラズマ活性化乳酸リンゲル点滴 (PAL) によるイネ幼苗の成長促進効果査読有り

橋爪博司, 水野寛子, 北野英己, 湯浅元気, 東野里江, 田中宏昌, 石川健治, 松本省吾, 榊原均, 前島正義, 仁川進, 水野正明, 堀勝

応用物理学会学術講演会講演予稿集 2019.2 巻 ( 0 ) 頁： 1895 - 1895 2019年9月

プラズマ処理によるイチゴ果実中の抗酸化物質量増加査読有り

橋爪博司, 坪田憲紀, 松本省吾, 湯浅元気, 伊藤昌文, 石川健治, 大熊隆之, 榊原均, 仁川進, 堀勝, 水野正明, 北野英己, 前島正義, 田中宏昌, 東野里江

応用物理学会学術講演会講演予稿集 2019.2 巻 ( 0 ) 頁： 1897 - 1897 2019年9月

イネ圃場における定期的な低温プラズマ処理による生育や収穫に対する検討 (II) 査読有り

橋爪博司, 北野英己, 水野寛子, 湯浅元気, 東野里江, 田中宏昌, 石川健治, 仁川進, 前島正義, 堀勝, 水野正明, 榊原均, 松本省吾

応用物理学会学術講演会講演予稿集 2019.2 巻 ( 0 ) 頁： 1896 - 1896 2019年9月

CH3Fの電子物性と解離査読有り

関根誠, 林俊雄, 堀勝, 石川健治

応用物理学会学術講演会講演予稿集 2019.2 巻 ( 0 ) 頁： 1837 - 1837 2019年9月

Atmospheric Pressure Plasma-Treated Carbon Nanowalls' Surface-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (CNW-SALDI-MS) 査読有り Open Access

Ohta, T; Ito, H; Ishikawa, K; Kondo, H; Hiramatsu, M; Hori, M

C-JOURNAL OF CARBON RESEARCH 5 巻 ( 3 ) 2019年9月

Miyajima, H; Ishikawa, K; Sekine, M; Hori, M

PLASMA PROCESSES AND POLYMERS 16 巻 ( 9 ) 2019年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

The developments in advanced interconnect technology for semiconductor logic devices for the mitigation of plasma-induced damage to low-dielectric-constant (low-k) materials, including fluorosilicate glass and carbon-doped silicon oxide is reviewed. The chemical bond structures of low-k materials are summarized to help mitigate the k value degradation caused by moisture uptake after plasma processes. Damage suppression is accomplished by integrating deposition chemistries, pattern etch transfer, and post-etch cleaning technologies. On the basis of analyses results, a discussion on the bond engineering of low-k materials and their degradation during plasma processing is given. Challenges facing low-k interconnect technology are also addressed.

DOI： 10.1002/ppap.201900039

Self-limiting reactions of ammonium salt in CHF3/O2 downstream plasma for thermal-cyclic atomic layer etching of silicon nitride 査読有り

Shinoda, K; Miyoshi, N; Kobayashi, H; Izawa, M; Saeki, T; Ishikawa, K; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 37 巻 ( 5 ) 2019年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology A Vacuum Surfaces and Films

Self-limiting reactions of ammonium salt in CHF<inf>3</inf>/O<inf>2</inf> downstream plasma were demonstrated for thermal-cyclic atomic layer etching (ALE) of Si<inf>3</inf>N<inf>4</inf>. In situ x-ray photoelectron spectroscopy analysis shows that an (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> by-product of the same thickness forms on Si<inf>3</inf>N<inf>4</inf> in a wide gas composition range. The (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> layer prevents etching of Si<inf>3</inf>N<inf>4</inf> during continuous plasma exposure in that wide range. The (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> layer was sublimated by heating, which was consistent with the result of the thermodynamic calculation. The reactions of the (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> layer in CHF<inf>3</inf>/O<inf>2</inf> downstream plasma are used for thermal-cyclic ALE of Si<inf>3</inf>N<inf>4</inf> with a newly developed 300-mm tool equipped with an in situ ellipsometer. It was confirmed that the amount etched per cycle saturates with respect to both plasma exposure time and infrared irradiation time.

DOI： 10.1116/1.5111663

Simultaneous achievement of antimicrobial property and plant growth promotion using plasma-activated benzoic compound solution 査読有り

Iwata, N; Gamaleev, V; Hashizume, H; Oh, JS; Ohta, T; Ishikawa, K; Hori, M; Ito, M

PLASMA PROCESSES AND POLYMERS 16 巻 ( 8 ) 2019年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

This study assesses a potential use of the recently developed nonthermal atmospheric pressure plasma technology in hydroponic plant cultivation. Two types of plasma-activated liquid solutions were compared, namely, l-Phenylalanine (l-Phe), which had a benzene ring structure, and l-Alanine (l-Ala), which did not have a benzene ring structure. Antimicrobial property and plant growth enhancement were simultaneously obtained when plasma-activated l-Phe was used. We found that the benzene ring structure in solution contributed to antimicrobial property. Further, colony forming unit assay indicated that 99% of Escherichia coli (E. coli) were eliminated after 24-h incubation and radish sprout growth increased by about 40% after 2 days of cultivation.

DOI： 10.1002/ppap.201900023

Gene Expression of Osteoblast-like Cells on Carbon-Nanowall as Scaffolds during Incubation with Electrical Stimulation 査読有り

Ichikawa T., Kondo H., Ishikawa K., Tsutsumi T., Tanaka H., Sekine M., Hori M.

ACS Applied Bio Materials 2 巻 ( 7 ) 頁： 2698 - 2702 2019年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Bio Materials

Nanostructured cell-culture scaffolds of carbon nanowalls (CNWs) were prepared by changing average wall-to-wall distances either 132 or 220 nm. Osteoblast-like cells (Saos-2) proliferated during 4 day incubation on the wider (220 nm) CNW scaffolds in the presence of electrical stimulation (ES). Differentiation gene expression levels of Runt-related transcription factor 2 (Runx2) and osteocalcin (OC) were suppressed after 10 day incubation, which indicated that the average wall-to-wall distances of the CNW scaffolds affect suppression of Runx2 and OC gene expression. This technique holds promise for controlling the differentiation of osteoblast-like cells.

DOI： 10.1021/acsabm.9b00178

Rethinking surface reactions in nanoscale dry processes toward atomic precision and beyond: a physics and chemistry perspective 査読有り国際共著 Open Access

Ishikawa, K; Ishijima, T; Shirafuji, T; Armini, S; Despiau-Pujo, E; Gottscho, RA; Kanarik, KJ; Leusink, GJ; Marchack, N; Murayama, T; Morikawa, Y; Oehrlein, GS; Park, S; Hayashi, H; Kinoshita, K

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SE ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

In this review, we discuss the progress of emerging dry processes with atomic precision. Researchers in the field of plasma processing and surface science have addressed the increasingly challenging demands of material selectivity by utilization of synergistic enhancement of etching or deposition. The discussion encompasses major challenges in the plasma science and technology community. The focus of the review is advances in atomic layer etching and area-selective deposition with activation or deactivation, especially in terms of materials scaling and variety. Control of high-aspect-ratio feature fabrication in semiconductor manufacturing and etched shapes of interior features at the nanoscale are needed. Issues related to profile distortion have received much attention. State-of-the-art techniques used in semiconductor manufacturing are reviewed and future challenges are outlined.

DOI： 10.7567/1347-4065/ab163e

Plasma-activated solution alters the morphological dynamics of supported lipid bilayers observed by high-speed atomic force microscopy 査読有り Open Access

Yamaoka, S; Kondo, H; Hashizume, H; Ishikawa, K; Tanaka, H; Hori, M

APPLIED PHYSICS EXPRESS 12 巻 ( 6 ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

The effects of plasma-activated Ringer's lactate solution (PAL) on supported lipid bilayers (SLBs) as a cell membrane model were investigated. PAL has selective killing effects on cancer cells. High-speed atomic force microscopy revealed alterations in the morphological dynamics of SLBs in PAL. SLB islands decreased approximately 20-fold faster in the presence of PAL compared to Ringer's lactate solution without plasma treatment. The effect of plasma treatment on the Ringer's lactate solution produced PAL components that account for the observed effects on cell membranes, such as removal of lipid molecules from the edges of SLBs and the following SLBs shrinkage.

DOI： 10.7567/1882-0786/ab1a58

Progress and perspectives in dry processes for emerging multidisciplinary applications: how can we improve our use of dry processes? 査読有り Open Access

Iwase, T; Kamaji, Y; Kang, SY; Koga, K; Kuboi, N; Nakamura, M; Negishi, N; Nozaki, T; Nunomura, S; Ogawa, D; Omura, M; Shimizu, T; Shinoda, K; Sonoda, Y; Suzuki, H; Takahashi, K; Tsutsumi, T; Yoshikawa, K; Ishijima, T; Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SE ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The non-thermal nature of chemical reactions in plasma chemistry is considered to be suitable for next-generation energy production from plasma-material syntheses and renewable sources. As emerging multidisciplinary applications, plasma medicine and plasma agriculture are currently topical applications that make use of atmospheric pressure plasmas. Here, we conduct a systematic review of the literature over the last 40 years to evaluate the history and progress of dry processes with regard to atmospheric pressure plasma technologies as well as material synthesis and thin-film deposition. In this review, selected breakthroughs are reviewed. Finally, near-future major challenges are addressed to encourage new multidisciplinary research across the plasma science and technology community.

DOI： 10.7567/1347-4065/ab163a

Progress and perspectives in dry processes for leading-edge manufacturing of devices: toward intelligent processes and virtual product development 査読有り

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SE ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Semiconductor device production has grown year on year, with high-volume manufacturing supported by advances in plasma processes. In plasma-based processing, ions and reactive species synergistically enhance chemical reactions, whose kinetics is in a nonequilibrium state in the region of the surface subjected to ion bombardment. To control such processing, methods for process monitoring, equipment control, modeling and simulation, and controlling plasma-induced damage, are required. Here, we conduct a systematic review of the literature over the last 40 years to evaluate the history and progress of dry processes in regard to intelligent process-control. We also address the challenges of implementing "virtual product development" utilizing information technology.

DOI： 10.7567/1347-4065/ab163b

Progress and perspectives in dry processes for nanoscale feature fabrication: fine pattern transfer and high-aspect-ratio feature formation 査読有り

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SE ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Dramatic advances are being made in dry processing technologies. Atomic scale precision below 10 nm is now possible with fine patterning technologies for high-volume manufacturing of semiconductor devices. The isotropic and anisotropic nature of both film deposition and etching is versatile for nanoscale fabrication of three-dimensional features, such as high-aspect-ratio (HAR) features. Here we conduct a systematic review of the literature over the last 40 years to evaluate the history and progress of dry processes with regard to fine pattern transfer, HAR feature formation, and multiple patterning as lithographic techniques. Finally, we address the major challenges shared across the plasma science and technology community.

DOI： 10.7567/1347-4065/ab1638

Electronic properties and primarily dissociation channels of fluoroethane compounds 査読有り

Hayashi, T; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SE ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Electronic properties of fluoroethane compounds except C<inf>2</inf>H<inf>5</inf>F, C<inf>2</inf>H<inf>4</inf>F<inf>2</inf>, CH<inf>3</inf>CF<inf>3</inf>, C<inf>2</inf>H<inf>2</inf>F<inf>4</inf>, and C<inf>2</inf>F<inf>6</inf> have not been reported. On the other hands, the physicochemical properties were reported for the usage as the alternative refrigerants. Dissociation channels in the process plasma for fluoroethane compounds were not fully discussed except 1,1,1,2-C<inf>2</inf>H<inf>2</inf>F<inf>4</inf>. Therefore we have investigated the electronic properties and primarily dissociation channels of fluoroethane compounds in the process plasma in semiconductor manufacturing, using computational chemistry. Positive and negative ionized states were investigated by density functional method and the excited states were investigated by EOMCCSD/aug-cc-pVDZ and TD-SCF CAM-B3LYP/aug-cc-pVDZ. It was generally shown through these investigations that C-C bond scission occurred by excitation and ionization and C-F bond scission occurred by excitation and electron attachment.

DOI： 10.7567/1347-4065/ab09ca

Polyethylene terephthalate (PET) surface modification by VUV and neutral active species in remote oxygen or hydrogen plasmas 査読有り国際共著

Zhang, Y; Ishikawa, K; Mozetic, M; Tsutsumi, T; Kondo, H; Sekine, M; Hori, M

PLASMA PROCESSES AND POLYMERS 16 巻 ( 6 ) 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

Polyethylene terephthalate (PET) are exposed either by VUV photons emitted from oxygen or hydrogen plasmas or by VUV photons and neutral active species from both plasmas. The water contact angle (WCA) of PET surface increased after treatment with H<inf>2</inf> VUV + H atoms, due to the cleavage of the oxygen-containing groups by VUV photons. The WCA decreased for the case of treatment with O<inf>2</inf> VUV + O-related neutral active species, leading to be released the polar groups like −COH or −COOH from the PET surface with a depth of less than about 10 nm. Oxygen-related neutrals etched the PET film and generated a rough surface which also contributed to the decrease in WCA however no bulk chemical structure obviously changed.

DOI： 10.1002/ppap.201800175

Laser-drilling formation of through-glass-via (TGV) on polymer-laminated glass 査読有り

Sato, Y; Imajyo, N; Ishikawa, K; Tummala, R; Hori, M

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS 30 巻 ( 11 ) 頁： 10183 - 10190 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Science Materials in Electronics

A three-dimensional (3D) glass integrated passive device (IPD) is an evolutionally advanced configuration to dramatically reduce the electronics form factor and manufacturing cost of current IPDs by introducing ultra-thin glass with through-glass-vias (TGVs). A defect-free TGV formation technology in polymer-laminated glass substrates is required to realize a highly reliable 3D glass IPD. This paper discusses mechanisms of each defect formation in the use of several types of lasers to explore suitable technology for defect-free drilling in polymer-laminated glass.

DOI： 10.1007/s10854-019-01354-5

Chemical bonding structure in porous SiOC films (k < 2.4) with high plasma-induced damage resistance 査読有り Open Access

Miyajima H., Masuda H., Watanabe K., Ishikawa K., Sekine M., Hori M.

Micro and Nano Engineering 3 巻頁： 1 - 6 2019年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Micro and Nano Engineering

The chemical bonding structure of porous low-k carbon-doped silicon oxide (SiOC) films (k < 2.4) was engineered using plasma-enhanced chemical vapor deposition and electron-beam curing. The high carbon concentration in the SiOC films with di-methyl bonds ([dbnd]Si(–]CH<inf>3</inf>)<inf>2</inf>) is crucial for resistance to plasma-induced damage (PID) and prevention of moisture uptake after the plasma treatment. The mix of di-methyl bonds is believed to be the key to protecting the films from PID because the films retain their hydrophobic characteristics even after plasma treatment. Thus, control of the ratio of di-methyl bonds to mono-methyl bonds ([tbnd]Si–]CH<inf>3</inf>) in the as-deposited SiOC film is necessary. Selection of trimethyl silane as a precursor for film matrix formation resulted in excellent control of this ratio to obtain highly reliable low-k/Cu interconnects for high-performance logic devices.

DOI： 10.1016/j.mne.2019.02.005

Effects of plasma shield plate design on epitaxial GaN films grown for large-sized wafers in radical-enhanced metalorganic chemical vapor deposition 査読有り

Isobe, Y; Sakai, T; Sugiyama, N; Mizushima, I; Suguro, K; Miyashita, N; Lu, Y; Wilson, AF; Kumar, DA; Ikarashi, N; Kondo, H; Ishikawa, K; Shimizu, N; Oda, O; Sekine, M; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 37 巻 ( 3 ) 2019年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B Nanotechnology and Microelectronics

Epitaxial growth of GaN films at a low temperature of 800 °C was studied in radical-enhanced metal-organic chemical vapor deposition, focusing on the discharge region of the plasma of a mixture of N<inf>2</inf> and H<inf>2</inf> gases. The effect of plasma confinement on the growth is crucial for realizing high crystal quality of grown GaN films, owing to the suppression of plasma-induced damage and decomposition of gallium precursors in the gaseous phase. By confined plasma in the discharge region using the plasma shield plates made of metal with multiple small holes effectively, GaN with a relatively flat surface was grown under conditions of higher V/III ratios. Epitaxial growth of GaN films was achieved by modifying the plate design and controlling the high V/III ratio using both the plasma-excitation power and the Ga precursor flow rate.

DOI： 10.1116/1.5083970

Erratum to “Chemical bonding structure in porous SiOC films (k < 2.4) with high plasma-induced damage resistance” (Micro and Nano Engineering (2019) 3 (1–6), (S2590007219300097), (10.1016/j.mne.2019.02.005)) 査読有り Open Access

Miyajima H., Masuda H., Watanabe K., Ishikawa K., Sekine M., Hori M.

Micro and Nano Engineering 3 巻頁： 92 - 92 2019年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Micro and Nano Engineering

The publisher regrets that we missed to publish the conflict of interest statement in the original article. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The publisher would like to apologise for any inconvenience caused.

DOI： 10.1016/j.mne.2019.05.004

Facile synthesis of SnO2-graphene composites employing nonthermal plasma and SnO2 nanoparticles-dispersed ethanol 査読有り

Borude, RR; Sugiura, H; Ishikawa, K; Tsutsumi, T; Kondo, H; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 52 巻 ( 17 ) 2019年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

The tin oxide (SnO <inf>2</inf> )-graphene composite was synthesized by the in-liquid plasma method using SnO <inf>2</inf> nanoparticles (average diameter ∼30 nm) dispersed ethanol as a precursor without providing external heat. As observed from scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the SnO <inf>2</inf> nanoparticles were distributed uniformly on flaky graphene sheets. The formation of SnO <inf>2</inf> and high crystalline graphene was supported by the Raman analysis and x-ray diffraction (XRD) studies. A facile, low-cost method operating at atmospheric pressure based on the in-liquid plasma technology can be utilized to fabricate SnO <inf>2</inf> -graphene composite using minimum precursors for future applications such as gas sensing devices and fuel cells.

DOI： 10.1088/1361-6463/ab03c4

Systematic diagnostics of the electrical, optical, and physicochemical characteristics of low-temperature atmospheric-pressure helium plasma sources 査読有り

Takeda, K; Yamada, H; Ishikawa, K; Sakakita, H; Kim, J; Ueda, M; Ikeda, J; Akimoto, Y; Kataoka, Y; Yokoyama, N; Ikehara, Y; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 52 巻 ( 16 ) 2019年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

The performance characteristics of two plasma sources, based on different types of discharge, were assessed. Three primary aspects of these sources were examined. These were electrical parameters (voltage and current flowing through a target), plasma parameters (gas temperature and electron density, determined using optical emission spectroscopy), and levels of gas-phase oxygen atoms (measured by vacuum ultraviolet absorption spectroscopy) and liquid-phase ▪OH radicals (generated by plasma treatment of water and detected using an electron spin resonance spin-trapping technique). As a result, there were few significant differences such as electron density, oxygen atom density, and gas temperature between the two plasma sources. However, the time-averaged electrical currents flowing to the target and the amount of liquid-phase ▪OH radicals showed a large difference, especially when the plume made contact with the target. Thus, many points of similarity but some differences in the two devices were found by the benchmarking study. These shall contribute to our understanding of the mechanisms for each consequence in medical applications.

DOI： 10.1088/1361-6463/aaff44

A 65-nm CMOS Fully Integrated Analysis Platform Using an On-Chip Vector Network Analyzer and a Transmission-Line-Based Detection Window for Analyzing Circulating Tumor Cell and Exosome 査読有り Open Access

Niitsu, K; Nakanishi, T; Murakami, S; Matsunaga, M; Kobayashi, A; Karim, NM; Ito, J; Ozawa, N; Hase, T; Tanaka, H; Sato, M; Kondo, H; Ishikawa, K; Odaka, H; Hasegawa, Y; Hori, M; Nakazato, K

IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 13 巻 ( 2 ) 頁： 470 - 479 2019年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Transactions on Biomedical Circuits and Systems

A fully integrated CMOS circuit based on a vector network analyzer and a transmission-line-based detection window for circulating tumor cell (CTC) and exosome analysis is presented for the first time. We have introduced a fully integrated architecture, which eliminates the undesired parasitic components and enables high-sensitivity, to analyze extremely low-concentration CTC in blood. The detection window was designed on the high-sensitive coplanar waveguide line. To validate the operation of the proposed system, a test chip was fabricated using 65-nm CMOS technology. Measurements were performed after adding a tiny lump of silicone or a droplet of water on its detection window. The measured results show S-21 degradation of-1.96 dB and-6.04 dB for the silicone and the droplet, respectively, at 1.4 GHz. In addition, in another measurement using magnetic beads, it is confirmed that the proposed circuit can analyze even low concentrations of 20 beads/μL. As well as microbeads, measurement with CTCs was successfully demonstrated.

DOI： 10.1109/TBCAS.2018.2882472

Effects of 3D structure on electrochemical oxygen reduction characteristics of Pt- nanoparticle-supported carbon nanowalls 査読有り

Imai, S; Naito, K; Kondo, H; Cho, HJ; Ishikawa, K; Tsutsumi, T; Sekine, M; Hiramatsu, M; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 52 巻 ( 10 ) 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

For polymer electrolyte fuel cell applications, effects of Pt-nanoparticle-supported 3D carbon nanostructures, i.e. carbon nanowalls (Pt/CNWs), on electrochemical characteristics were determined by alternating current impedance analysis of resistive elements, which contribute to the oxygen reduction reaction. CNWs were fabricated by radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD), and Pt catalysts were formed on the template of CNWs by supercritical fluid metalorganic chemical fluid deposition. CNWs of different wall densities were synthesized during RI-PECVD by varying the deposition pressure. The resistive elements can be consisted of three regions with different corresponding frequencies, and the resistive elements of mass diffusion, which showed up in the lowest frequency region of less than 100 Hz, increased as the wall density of CNWs increased. It was found that the wall density of CNWs was one of the essential parameters of Pt/CNWs for the electrochemical reaction involving the fluid flow and the mass transfer of active materials.

DOI： 10.1088/1361-6463/aaf8e0

Control of sp2-C cluster incorporation of amorphous carbon films grown by H-radical-injection CH4/H2 plasma-enhanced chemical vapor deposition 査読有り

Sugiura, H; Jia, LY; Ohashi, Y; Kondo, H; Ishikawa, K; Tsutsumi, T; Hayashi, T; Takeda, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 3 ) 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Amorphous carbon (a-C) thin films were deposited under the control of C<inf>2</inf> radical density using radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD) with CH<inf>4</inf>/H<inf>2</inf> plasma. By actinometric monitoring of C<inf>2</inf> emission intensities, the plasma parameters were precisely controlled by changing in CH<inf>4</inf>-containing plasma excitation power independent of H<inf>2</inf> plasma excitation. The control of the incorporation of sp2-C clusters in the a-C films during the a-C film depositions is demonstrated by tailoring Raman positions vs. full widths at half maxima for the G band around 1580 cm-1 to the RI-PECVD parameters.

DOI： 10.7567/1347-4065/aafd49

Effects of BCl3 addition to Cl2 gas on etching characteristics of GaN at high temperature 査読有り

Tanide, A; Nakamura, S; Horikoshi, A; Takatsuji, S; Kohno, M; Kinose, K; Nadahara, S; Ishikawa, K; Sekine, M; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 37 巻 ( 2 ) 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology B Nanotechnology and Microelectronics

Gallium nitride films were etched at 400 °C and 20 Pa with a radio-frequency-generated Cl<inf>2</inf>-BCl<inf>3</inf> mixed plasma. While dog-legged profiles were obtained by plasma etching using pure Cl<inf>2</inf>, straight sidewall shapes were achieved through BCl<inf>3</inf> gas addition into the Cl<inf>2</inf> plasma by suppressing the plasma-induced damage on the etched surface. Etching by-products containing boron on the etched surface affected the etch rate. Smooth etched profiles were obtained by controlling the redeposition of by-products of boron and chlorine compounds, particularly for substrate temperatures above 230 °C.

DOI： 10.1116/1.5082345

Effects of Ion Bombardment Energy Flux on Chemical Compositions and Structures of Hydrogenated Amorphous Carbon Films Grown by a Radical-Injection Plasma-Enhanced Chemical Vapor Deposition 査読有り Open Access

Sugiura, H; Kondo, H; Tsutsumi, T; Ishikawa, K; Hori, M

C-JOURNAL OF CARBON RESEARCH 5 巻 ( 1 ) 2019年3月

Electrochemical Reaction in Hydrogen Peroxide and Structural Change of Platinum Nanoparticle-Supported Carbon Nanowalls Grown Using Plasma-Enhanced Chemical Vapor Deposition 査読有り Open Access

Tomatsu, M; Hiramatsu, M; Kondo, H; Ishikawa, K; Tsutsumi, T; Sekine, M; Hori, M

C-JOURNAL OF CARBON RESEARCH 5 巻 ( 1 ) 2019年3月

青果物栽培における低温プラズマ処理の品質への効果査読有り

堀勝, 橋爪博司, 松本省吾, 湯浅元気, 田中宏昌, 榊原均, 東野里江, 水野正明, 北野英己, 坪田憲紀, 仁川進, 伊藤昌文, 前島正義, 大熊隆之, 石川健治

応用物理学会学術講演会講演予稿集 2019.1 巻 ( 0 ) 頁： 1678 - 1678 2019年2月

イネ種子への低温プラズマ照射による成長促進効果査読有り

水野寛子, 木下悟, 湯浅元気, 田中宏昌, 榊原均, 北野英己, 石川健治, 前島正義, 松本省吾, 東野里江, 仁川進, 水野正明, 橋爪博司, 堀勝

応用物理学会学術講演会講演予稿集 2019.1 巻 ( 0 ) 頁： 1676 - 1676 2019年2月

種子へ低温プラズマ照射したイネ苗の環境制御下における栽培査読有り

松本省吾, 橋爪博司, 北野英己, 湯浅元気, 東野里江, 水野寛子, 木下悟, 田中宏昌, 榊原均, 仁川進, 前島正義, 水野正明, 堀勝, 石川健治

応用物理学会学術講演会講演予稿集 2019.1 巻 ( 0 ) 頁： 1677 - 1677 2019年2月

イネ圃場における定期的な低温プラズマ処理による生育や収穫に対する検討査読有り

橋爪博司, 北野英己, 湯浅元気, 東野里江, 水野寛子, 田中宏昌, 石川健治, 松本省吾, 榊原均, 前島正義, 水野正明, 仁川進, 堀勝

応用物理学会学術講演会講演予稿集 2019.1 巻 ( 0 ) 頁： 1675 - 1675 2019年2月

Etching reactions of Si, SiO2, and SiN films using with hydrofluorocarbon compounds 査読有り

Kondo Hiroki, Sekine Makoto, Hori Masaru, Ni Jiawei, Hayashi Toshio, Ishikawa Kenji, Tsutsumi Takayoshi

JSAP Annual Meetings Extended Abstracts 2019.1 巻 ( 0 ) 頁： 1630 - 1630 2019年2月

Non-thermal plasma-activated medium modified metabolomic profiles in the glycolysis of U251SP glioblastoma 査読有り

Kurake, N; Ishikawa, K; Tanaka, H; Hashizume, H; Nakamura, K; Kajiyama, H; Toyokuni, S; Kikkawa, F; Mizuno, M; Hori, M

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS 662 巻頁： 83 - 92 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Archives of Biochemistry and Biophysics

Non-equilibrium atmospheric pressure plasma (NEAPP) is a mixture of radicals, electrons, anions, cations and light at near body temperature. Plasma-activated medium (PAM) is realized using NEAPP provided by engineered devices and irradiated to a cell culture medium for a period of 600 s. Glioblastoma cells U251SP cultivated in PAM previously indicated that antitumor effects induced PAM-specific apoptotic cell-death. Metabolomic profiles of a hundred intracellular metabolites were analyzed using capillary electrophoresis mass spectrometry. The metabolomic profiles of the PAM-treated U251SP cells were changed significantly with inhibition of the glycolysis pathway and with enhancement of the pentose phosphate pathway.

DOI： 10.1016/j.abb.2018.12.001

Remotely floating wire-assisted generation of high-density atmospheric pressure plasma and SF6-added plasma etching of quartz glass 査読有り

Nguyen, TTN; Sasaki, M; Odaka, H; Tsutsumi, T; Ishikawa, K; Hori, M

JOURNAL OF APPLIED PHYSICS 125 巻 ( 6 ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

High-density and large-volume atmospheric pressure plasma can be extended remotely by placing a long floating wire inside an Ar-gas flowing quartz tube connected with an inductively coupled coil. The discharge quartz tubes were categorized into three I-shaped tubes and one L-shaped tube. The influence of the geometrical design on plasma properties was investigated. Using the floating wire-assisted L tube, an electron density of 10 14 cm -3 and a gas temperature less than 850 K were obtained at the downstream remote region. That is where the Ar plasma plume blew out from the slit at the bottom of the floating wire-assisted L tube at a distance of 140 mm from the coil center, when 100 W of a very high-frequency power (100 MHz) was applied to the inductively coupled coil. The applicability of this new L-type plasma source for large-area glass etching with a high etch rate was explored. At the remote region where the Ar plasma plume blew out of the slit of the L tube, SF <inf>6</inf> gas was added for etching a quartz glass plate. Glass etching could be obtained over a large area of 15 mm × 20 mm with a maximum etch rate of 2 μm/min and a volume etch rate of 0.3 mm 3 /min.

DOI： 10.1063/1.5081875

Liquid dynamics in response to an impinging low-temperature plasma jet 査読有り国際共著

Brubaker, TR; Ishikawa, K; Kondo, H; Tsutsumi, T; Hashizume, H; Tanaka, H; Knecht, SD; Bilén, SG; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 52 巻 ( 7 ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

The liquid-phase behavior induced by an atmospheric pressure plasma jet impinging onto water-based solutions was experimentally investigated. An increase in cavity size and circulation size resulting from an increase in impact force of the plasma jet with respect to a helium gas jet were observed through particle image velocimetry and cavity measurements. The increase in circulation size due to plasma discharge was larger than the increase solely due to an increase in jet impact force, suggesting additional shear along the liquid free surface evidenced by schlieren images of plasma-induced gas flow adherence after impingement. Liquid evaporation rate increased and mean liquid temperature decreased due to plasma effects on jet behavior. Plasma-induced decreases in liquid pH and temperature were contained within the circulation flow, leading to strong pH and temperature gradients within the liquid volume. Areas treated by the jet became acidic and remained more acidic than other portions of the liquid due to circulation vortices, highlighting the consequences of jet and liquid vessel parameters for plasma jet-liquid applications.

DOI： 10.1088/1361-6463/aaf460

Effect of electrical stimulation on proliferation and bone-formation by osteoblast-like cells cultured on carbon nanowalls scaffolds 査読有り Open Access

Ichikawa, T; Tanaka, S; Kondo, H; Ishikawa, K; Tsutsumi, T; Sekine, M; Hori, M

APPLIED PHYSICS EXPRESS 12 巻 ( 2 ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Carbon nanowalls (CNWs) were synthesized by radical injection plasma-enhanced chemical vapor deposition and used as scaffolds for cell culture. The proliferation of osteoblast-like cells (Saos-2) was enhanced on the CNW scaffold upon electrical stimulation (ES) with 10 Hz square pulses at a current of 226 nA. However, after incubation with ES for 10 d, differentiation of the cells toward bone formation was suppressed.

DOI： 10.7567/1882-0786/aaf469

Adhesion enhancement and amine reduction using film redeposited at the interface of a stack of plasma-enhanced CVD dielectrics for Cu/low-k interconnects 査読有り

Miyajima, H; Watanabe, K; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 2 ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The dielectric interface for a stack of SiOC and SiCN films in Cu/low-k interconnects is engineered using Ar plasma pretreatment of the top surface of SiCN, which prevents oxidization during SiOC film deposition. Oxidized SiCN causes delamination of the SiOC film and resist poisoning through amines generated during resist baking, which can lead to undeveloped photoresist. The Ar plasma pretreatment in the plasma-enhanced chemical vapor deposition chamber modifies the interface by redepositing a thin pre-coated SiOC film from the upper electrode surface. This redeposited SiOC film acts as a buffer for oxygen plasma during SiOC film deposition.

DOI： 10.7567/1347-4065/aafb5b

Narrow free-standing features fabricated by top-down self-limited trimming of organic materials using precisely temperature-controlled plasma etching system 査読有り

Fukunaga, Y; Tsutsumi, T; Kondo, H; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 2 ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Anisotropic etching was conducted in H<inf>2</inf>/N<inf>2</inf> plasma. Subsequently, etched organic features were trimmed for a period longer than 300 s, while the substrate temperature was precisely controlled within ±1.2 °C of a set temperature. This temperature control was achieved by automatically-operated on-off sequences of the plasma excitation and bias powers. The free-standing feature, with a width narrower than 12 nm, was fabricated in a self-limiting manner. This manner was achieved by a balance moving between the etching and adsorption of the H and N atoms in the H<inf>2</inf>/N<inf>2</inf> plasma, transited under a constant substrate temperature of 100 °C.

DOI： 10.7567/1347-4065/aaf92a

Modifications of surface and bulk properties of magnetron-sputtered carbon films employing a post-treatment of atmospheric pressure plasma 査読有り

Borude, RR; Sugiura, H; Ishikawa, K; Tsutsumi, T; Kondo, H; Han, JG; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SA ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Control of the bonding structure in carbon materials is achieved by a post-treatment of atmospheric pressure plasma (APP) for magnetron-sputtered carbon films. The APP post-treatment changes the films morphologically owing to the removal and modification of sp2 bonds on the basis of the near edge X-ray absorption fine structure analysis of sp2 contents. By APP post-treatment, the resulting changes in surface and bulk properties modify the optical and electrical properties of the carbon films. The control of the film properties can be utilized for various applications, such as gas sensors and solar cells.

DOI： 10.7567/1347-4065/aaec87

Hetero-epitaxial growth of a GaN film by the combination of magnetron sputtering with Ar/Cl2 gas mixtures and a separate supply of nitrogen precursors from a high density radical source 査読有り

Tanide, A; Nakamura, S; Horikoshi, A; Takatsuji, S; Kohno, M; Kinose, K; Nadahara, S; Nishikawa, M; Ebe, A; Ishikawa, K; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SA ) 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Hetero-epitaxial growth of a gallium nitride (GaN) film on an AlN(0 0 0 1) buffer layer on a sapphire(0 0 0 1) substrate was demonstrated by supplying gallium precursors and nitrogen radicals separately from two individually operated plasma sources to control the V/III supplying ratio precisely. The sources were a reactive Ar-Cl<inf>2</inf>-mixture plasma sputtering of a gallium target and a remote low inductance antenna (LIA) for N<inf>2</inf>-H<inf>2</inf> inductively coupled-plasma. Lateral growth of the GaN film was observed in 0.5%-Cl<inf>2</inf>-added Ar sputtering at a low growth temperature of 670 ?C, whilst the growth mode coalesced at temperatures lower than 600 ?C. With more than 2.0% of Cl<inf>2</inf>, no film was deposited due to etching by the reactive chlorine whenever the temperature was at 500 ?C. At the growth temperature of 670 ?C, crystallinity with narrow a X-ray rocking curve GaN (0 0 0 2) was obtained at the condition of 0.5% Cl<inf>2</inf> and 27.4% N<inf>2</inf>, even though the background pressure was 10-4 Pa.

DOI： 10.7567/1347-4065/aaeb39

Single-Step, Low-Temperature Simultaneous Formations and in Situ Binding of Tin Oxide Nanoparticles to Graphene Nanosheets by In-Liquid Plasma for Potential Applications in Gas Sensing and Lithium-Ion Batteries 査読有り

Borude, RR; Sugiura, H; Ishikawa, K; Tsutsumi, T; Kondo, H; Ikarashi, N; Hori, M

ACS APPLIED NANO MATERIALS 2 巻 ( 2 ) 頁： 649 - 654 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Nano Materials

The in situ binding of tin oxide (SnO<inf>2</inf>) nanoparticles (SNp) and graphene nanosheets (GNs) that synthesized simultaneously in single-step atmospheric-pressure processing was achieved at a low temperature by employing in-liquid plasma in a solution of tin chloride (SnCl<inf>2</inf>·2H<inf>2</inf>O) in ethanol as the only precursor. Transmission electron microscopy, Raman analysis, and X-ray diffraction revealed the composite (SNp/GNs) synthesis with SNp of sizes 2-3 nm, which were distributed uniformly and attached to both sides of the GNs. The SNp/GNs composite synthesis was provided by the simple, low-cost, single-processing method of the in-liquid plasma for future gas-sensing and lithium-ion battery applications.

DOI： 10.1021/acsanm.8b02201

Pt nanoparticle-supported carbon nanowalls electrode with improved durability for fuel cell applications using C2F6/H2 plasma-enhanced chemical vapor deposition 査読有り Open Access

Imai, S; Kondo, H; Hyungjun, C; Ishikawa, K; Tsutsumi, T; Sekine, M; Hiramatsu, M; Hori, M

APPLIED PHYSICS EXPRESS 12 巻 ( 1 ) 2019年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

The electrochemical durability of Pt nanoparticles-supported carbon nanowalls (Pt/CNWs) determined from potential cycle tests was 88% performance after 20 000 cycles and 50% performance around 140 000 cycles when the CNWs were fabricated by the C <inf>2</inf> F <inf>6</inf> /H <inf>2</inf> plasma-enhanced chemical vapor deposition system (C <inf>2</inf> F <inf>6</inf> -CNWs). Even after the extended start/stop-simulation tests of fuel cell Pt/C <inf>2</inf> F <inf>6</inf> -CNWs, Pt was aggregated; however, the morphological structure of the CNWs was maintained and no corrosion was evident from scanning electron microscopy observations and Raman analysis. For graphene-based catalyst supports, i.e., the Pt/C <inf>2</inf> F <inf>6</inf> -CNWs, graphene crystallinity is essential to extend electrochemical durability by inhibiting corrosion during fuel cell operation.

DOI： 10.7567/1882-0786/aaf0ab

Batch Fabrication of Nano-Gap Electrode Array Using Photo-Patterning and Resist UV-Curing

Nguyen Hai Minh, Kumeuchi Mako, Kumagai Shinya, Ishikawa Kenji, Hori Masaru, Sasaki Minoru

IEEJ Transactions on Sensors and Micromachines 139 巻 ( 1 ) 頁： 27 - 28 2019年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：The Institute of Electrical Engineers of Japan

A nano-gap electrode array is batch-fabricated based on photolithography. A high resolution is obtained by using an over-hanging resist cover on the under-etched metal film. The process includes two-time mask-patterning. The first photoresist is UV-cured, allowing second patterning without degrading the first pattern. A nano-gap width of 237±63 nm is obtained from a 704-electrode array with an yield of 97%.

DOI： 10.1541/ieejsmas.139.27

Molecular mechanisms of non-thermal plasmainduced effects in cancer cells 査読有り Open Access

Tanaka, H; Mizuno, M; Ishikawa, K; Toyokuni, S; Kajiyama, H; Kikkawa, F; Hori, M

BIOLOGICAL CHEMISTRY 400 巻 ( 1 ) 頁： 87 - 91 2019年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Biological Chemistry

Plasma is the fourth state of matter with higher energy than gas; non-thermal plasma (NTP) is currently available. As NTP is useful in sterilization, promoting wound healing and cancer treatments, the molecular mechanisms of plasma-induced effects in living cells and microorganisms are of significant interest in plasma medicine with medical-engineering collaboration. Molecular mechanisms of plasma-induced effects in cancer cells will be described in this minireview. Both direct and indirect methods to treat cancer cells with NTP have been developed. NTP interacts directly with not only cancer cells but also the liquids surrounding cancer cells and the immune cells that target them. Reactive oxygen and nitrogen species play key roles in NTP-induced effects; however, other mechanisms have been suggested. The complex interactions between NTP, cells and liquids have been extensively studied. In the future, details regarding NTP-induced effects on gene regulatory networks, signaling networks, and metabolic networks will be elucidated.

DOI： 10.1515/hsz-2018-0199

Single-cell microscopic raman spectroscopy for rapid microbial detection 査読有り

Onoshima D., Uchida K., Yukawa H., Ishikawa K., Hori M., Baba Y.

23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2019 頁： 1374 - 1375 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2019

We present a study of microbial Raman spectroscopy towards optimal approach of rapid microbiological methods (RMMs). Raman spectra of single microorganism cells were measured and analyzed by data clustering to identify the microbial species without culturing for colony formation.

DOI： 10.1002/ppap.201900023

Effect of N2/H2 plasma on GaN substrate cleaning for homoepitaxial GaN growth by radical-enhanced metalorganic chemical vapor deposition (REMOCVD) 査読有り Open Access

Amalraj, FW; Dhasiyan, AK; Lu, Y; Shimizu, N; Oda, O; Ishikawa, K; Kondo, H; Sekine, M; Ikarashi, N; Hori, M

AIP ADVANCES 8 巻 ( 11 ) 2018年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Aip Advances

We developed a new method of GaN growth using Radical-Enhanced Metalorganic Chemical Vapor Deposition (REMOCVD) technology by which Gallium Nitride (GaN) grows at low temperatures without ammonia gas. In this method, we investigated the effect of N<inf>2</inf>/H<inf>2</inf> plasma on the GaN substrate surface cleaning prior to the growth of homoepitaxial GaN. In-situ reflection high-energy electron diffraction (RHEED) and atomic force microscope (AFM) were used to investigate the surface morphology of the cleaned GaN substrates. The interface between GaN substrate and homoepitaxially grown GaN by REMOCVD was evaluated by transmission electron microscope and the crystal quality was evaluated by X-ray diffraction. The in-situ N<inf>2</inf>/H<inf>2</inf> plasma cleaning at 600 °C shows a smooth surface morphology with streak diffraction lines observed by RHEED. Since the homoepitaxial growth of GaN was performed at 800 °C, the cleaned GaN substrate temperature was ramped up from 600 °C to 800 °C with and without plasma exposure to compare the effect of plasma. Homoepitaxially grown GaN on GaN substrates whose temperature was ramped up with plasma exposure showed good crystal quality with no threading dislocations at the interface. It was found that N<inf>2</inf>/H<inf>2</inf> plasma plays a significant role in the GaN surface cleaning for good quality crystal growth.

DOI： 10.1063/1.5050819

Reaction mechanisms between chlorine plasma and a spin-on-type polymer mask for high-temperature plasma etching 査読有り

Zhang, Y; Imamura, M; Ishikawa, K; Tsutsumi, T; Kondo, H; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 10 ) 2018年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

To satisfy the requirement for mask materials in high-temperature plasma etching, a novolac-based polymer mask was evaluated during high-temperature Cl<inf>2</inf> plasma etching. Although the etch rate of 8 nm/min was rather high at a low temperature of 230 °C, it decreased with the increase in temperature. The aromatic ring structures were significantly modified by vacuum ultraviolet (VUV) and Cl radicals during the processes above 300 °C and transformed to a highly cross-linked amorphous carbon (a-C) layer at the surface confirmed from infrared and Raman spectra. The formation of this a-C layer improved the etching resistance of the polymer mask. On the other hand, surface roughness can also be improved after processes above 300 °C corresponding to the generation of the a-C layer. Therefore, this polymer mask is a promising candidate for high-temperature plasma etching with high etch resistance, and a smooth surface can be obtained during processes above 300 °C.

DOI： 10.7567/JJAP.57.106502

Elevated-temperature etching of gallium nitride (GaN) in dual-frequency capacitively coupled plasma of CH4/H2 at 300-500 °C 査読有り

Kako, T; Liu, ZC; Ishikawa, K; Kondo, H; Oda, O; Sekine, M; Hori, M

VACUUM 156 巻頁： 219 - 223 2018年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Vacuum

Elevated-temperature etching with CH<inf>4</inf>/H<inf>2</inf> plasma chemistry at 300 °C improves damage-less optical properties of GaN, solving issues of degradation on near-band-edge photoluminescence intensity on plasma etching at lower temperatures than 300 °C. Damage-less etching properties in a smooth surface, high photoluminescence intensity, and substantial stoichiometric ratio of gallium and nitrogen were obtained when the CH<inf>4</inf>/H<inf>2</inf> chemistry with substrate temperatures at 300–500 °C.

DOI： 10.1016/j.vacuum.2018.07.040

Cytotoxic effects of plasma-irradiated fullerenol 査読有り

Kanno, D; Tanaka, H; Ishikawa, K; Hashizume, H; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 51 巻 ( 37 ) 2018年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

Fullerenol dissolved in water was irradiated with a non-equilibrium atmospheric pressure plasma. Plasma irradiation altered the fullerenol solution by introducing carbonyl groups, ether bonds, and intercalated nitrate anions. The resulting plasma-irradiated fullerenol (PF) was added in cell culture medium. PF-supplemented medium exhibited a cytotoxic effect on HeLa cells. Notably, HeLa cells cultured in the PF-added cell culture medium generated intracellular reactive oxygen and nitrogen species, such that the endocytosis of PF induced the apoptotic cell death. The cytotoxic effect inducing apoptosis was found in the PF-supplemented medium.

DOI： 10.1088/1361-6463/aad510

大気圧プラズマ処理による異種材料接合招待有り査読有り

近藤博基, 堤隆嘉, 石川健治, 関根誠, 堀勝

化学工学 82 巻 ( 9 ) 2018年9月

New hopes for plasma-based cancer treatment 査読有り Open Access

Hiromasa Tanaka, Masaaki Mizuno, Kenji Ishikawa, Shinya Toyokuni, Hiroaki Kajiyama, Fumitaka Kikkawa, and Masaru Hori

Plasma 1 巻 ( 1 ) 頁： 150 - 155 2018年9月

Real-time control of a wafer temperature for uniform plasma process 査読有り

Tsutsumi T., Fuknaga Y., Ishikawa K., Kondo H., Sekine M., Hori M.

IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings 2018-December 巻 2018年7月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings

Our developed non-contact method for measurement of temperature of silicon (Si) wafer by using autocorrelation-type fourier domain low coherence interferometer has advantageous in accuracy and rapid response. We demonstrate measurements in temperature for Si wafer at real-time during plasma process and in estimation of heat flux to the wafer from plasma, involving heats balanced plasma source and conductive loss in Si. The analysis indicated that other heat sources like the chamber parts with relatively high temperature impact on the duty ratio during the process with feedback control of the wafer teperture.

DOI： 10.1109/ISSM.2018.8651183

Temperature dependence on plasma-induced damage and chemical reactions in GaN etching processes using chlorine plasma 査読有り

Liu, ZC; Ishikawa, K; Imamura, M; Tsutsumi, T; Kondo, H; Oda, O; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Plasma-induced damage (PID) on GaN was optimally reduced by high-temperature chlorine plasma etching. Energetic ion bombardments primarily induced PID involving stoichiometry, surface roughness, and photoluminescence (PL) degradation. Chemical reactions under ultraviolet (UV) irradiation and chlorine radical exposure at temperatures higher than 400 °C can be controlled by taking into account the synergism of simultaneous photon and radical irradiations to effectively reduce PID.

DOI： 10.7567/JJAP.57.06JD01

Progress in nanoscale dry processes for fabrication of high-aspect-ratio features: How can we control critical dimension uniformity at the bottom? 査読有り国際共著 Open Access

Ishikawa, K; Karahashi, K; Ishijima, T; Cho, SI; Elliott, S; Hausmann, D; Mocuta, D; Wilson, A; Kinoshita, K

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

In this review, we discuss the progress of emerging dry processes for nanoscale fabrication of high-aspect-ratio features, including emerging design technology for manufacturability. Experts in the fields of plasma processing have contributed to addressing the increasingly challenging demands of nanoscale deposition and etching technologies for high-aspect-ratio features. The discussion of our atomic-scale understanding of physicochemical reactions involving ion bombardment and neutral transport presents the major challenges shared across the plasma science and technology community. Focus is placed on advances in fabrication technology that control surface reactions on three-dimensional features, as well as state-of-the-art techniques used in semiconductor manufacturing with a brief summary of future challenges.

DOI： 10.7567/JJAP.57.06JA01

Low-autofluorescence fluoropolymer membrane filters for cell filtration 査読有り Open Access

Kihara, N; Kuboyama, D; Onoshima, D; Ishikawa, K; Tanaka, H; Ozawa, N; Hase, T; Koguchi, R; Yukawa, H; Odaka, H; Hasegawa, Y; Baba, Y; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

A fluoropolymer membrane filter with through-holes was fabricated by photolithographic patterning and the dry etching method. 380,000 highly packed through-holes, each with a diameter of 7 µm were able to cover a whole area with a diameter of 13 mm. Ethylene tetrafluoroethylene (ETFE) was used as the membrane, which was suitable for the fluorescence detection of rare cells such as circulating tumor cells (CTCs) in human blood. The device fabrication for the size based capture of rare cells in blood such as CTCs is realized in this study.

DOI： 10.7567/JJAP.57.06JF03

Impact of helium pressure in arc plasma synthesis on crystallinity of single-walled carbon nanotubes 査読有り

Ando, A; Takeda, K; Ohta, T; Ito, M; Hiramatsu, M; Ishikawa, K; Kondo, H; Sekine, M; Suzuki, T; Inoue, S; Ando, Y; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Single-walled carbon nanotubes (SWNTs) were synthesized with a high growth rate by an arc plasma method employing the electrodes made from a Ni–Y mixture catalyst. In a previous study, it was reported that the monitoring of high-crystallinity SWNT growth enabled the evaluation of the results of the optical emission spectroscopy (OES) of C<inf>2</inf>, Ni, and Y. Here, the impact of helium pressure of arc plasma on the high crystallinity of SWNTs was determined by considering the high intensity ratios of catalytic metals over C<inf>2</inf> emissions at low helium pressures in the arc plasma.

DOI： 10.7567/JJAP.57.06JF01

Effects of gas residence time of CH4/H2 on sp2 fraction of amorphous carbon films and dissociated methyl density during radical-injection plasma-enhanced chemical vapor deposition 査読有り

Sugiura, H; Jia, LY; Kondo, H; Ishikawa, K; Tsutsumi, T; Hayashi, T; Takeda, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Quadruple mass spectrometric measurements of CH<inf>3</inf> density during radical-injection plasma-enhanced chemical vapor deposition to consider the sp2 fraction of amorphous carbon (a-C) films were performed. The sp2 fraction of the a-C films reached a minimum of 46%, where the CH<inf>3</inf> density was maximum for a residence time of 6 ms. The sp2 fraction of the a-C films was tailored with the gaseous phase CH<inf>3</inf> density during the deposition. This knowledge is useful for understanding the formation mechanism of bonding structures in the a-C films, which enables the precise control of their electronic properties.

DOI： 10.7567/JJAP.57.06JE03

Dry Process FOREWORD 査読有り

Karahashi, K; Kinoshita, K; Higashi, S; Ishikawa, K; Ishijima, T; Kuboi, N

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

Dissociative properties of 1,1,1,2-tetrafluoroethane obtained by computational chemistry 査読有り

Hayashi, T; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 6 ) 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The electronic properties and dissociative channels of the alternative to the CCl<inf>2</inf>F<inf>2</inf> (CFC-12) refrigerant, 1,1,1,2-tetrafluoroethane (HFC-134a) with a low global warming potential (GWP, 1430), were revealed by computational chemistry. The results show that CF<inf>3</inf>+ and CHF<inf>2</inf>+ ions are mainly produced by ionization. The CF<inf>3</inf>CH<inf>2</inf>+ ion is produced by ion pair formation and by direct ionization in the energy region higher than approximately 15 eV, but also in small amounts by the ionization of the dissociated CF<inf>3</inf>CH<inf>2</inf> radical. This information is useful for etching process engineers in leading-edge semiconductor manufacturing.

DOI： 10.7567/JJAP.57.06JC02

Nanographene synthesized in triple-phase plasmas as a highly durable support of catalysts for polymer electrolyte fuel cells 査読有り

Amano, T; Kondo, H; Takeda, K; Ishikawa, K; Hiramatsu, M; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 4 ) 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Nanographene was synthesized in triple-phase plasmas comprising a gaseous phase, a gas-liquid boundary layer, and an in-liquid phase using a setup in which one electrode was placed in the gaseous phase while the other was immersed in the liquid phase. The triple-phase plasmas were generated using a pure alcohol, such as ethanol, 1-propanol, or 1-butanol, by applying a high voltage to a pair of electrodes made of copper or graphite. The nanographene synthesized using ethanol had high durability and thus could serve as a catalyst support in polymer electrolyte fuel cells (PEFCs). The PEFCs exhibited low degradation rates in the high-potential cycle test of a half-cell, as a result of which, a loss of only 10% was observed in the effective electrochemical surface area of Pt, even after 10,000 cycles.

DOI： 10.7567/JJAP.57.045101

Oxygen reduction reaction properties of nitrogen-incorporated nanographenes synthesized using in-liquid plasma from mixture of ethanol and iron phthalocyanine 査読有り

Amano, T; Kondo, H; Takeda, K; Ishikawa, K; Hiramatsu, M; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 4 ) 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Nanographenes were synthesized using in-liquid plasma from a mixture of iron phthalocyanine and ethanol. In a previous study, micrometer-scale flakes with nitrogen incorporation were obtained. A nonprecious metal catalytic activity was observed with 3.13 electrons in an oxygen reduction reaction under an acidic solute condition. Large-surface-area, high-graphene-crystallinity, and iron-carbon-bonding sites were found owing to a high catalytic activity in Fe-N/nanographene.

DOI： 10.7567/JJAP.57.040303

Cytotoxicity of cancer HeLa cells sensitivity to normal MCF10A cells in cultivations with cell culture medium treated by microwave-excited atmospheric pressure plasmas 査読有り

Takahashi, Y; Taki, Y; Takeda, K; Hashizume, H; Tanaka, H; Ishikawa, K; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 51 巻 ( 11 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

Cytotoxic effects of human epithelial carcinoma HeLa cells sensitivity to human mammary epithelial MCF10A cells appeared in incubation with the plasma-activated medium (PAM), where the cell culture media were irradiated with the hollow-shaped contact of a continuously discharged plasma that was sustained by application of a microwave power under Ar gas flow at atmospheric pressure. The discharged plasma had an electron density of 7

DOI： 10.1088/1361-6463/aaab09

Free radical generation by non-equilibrium atmospheric pressure plasma in alcohol-water mixtures: an EPR-spin trapping study 査読有り

Uchiyama, H; Ishikawa, K; Zhao, QL; Andocs, G; Nojima, N; Takeda, K; Krishna, MC; Ishijima, T; Matsuya, Y; Hori, M; Noguchi, K; Kondo, T

JOURNAL OF PHYSICS D-APPLIED PHYSICS 51 巻 ( 9 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

Free radical species in aqueous solution - various alcohol-water reaction mixtures - by exposure to non-equilibrium cold atmospheric pressure Ar plasma (CAP), were monitored using electron paramagnetic resonance spin-trapping techniques with 3, 5-dibromo-4-nitrosobenzene sulfonate as a water soluble nitroso spin trap. The major radical species were formed by H-abstraction from alcohol molecules due to •OH radicals. In the ethanol-water mixture •CH<inf>2</inf>CH<inf>2</inf>OH produced by H abstraction from CH<inf>3</inf> group of the ethanol and •CH<inf>3</inf> radicals were detected. The latter was due to the decomposition of unstable CH<inf>3</inf>•CHOH to form the •CH<inf>3</inf> radicals and the stable formaldehyde by C-C bond fission. These intermediates are similar to those observed by reaction with •OH radicals generation in the H<inf>2</inf>O<inf>2</inf>-UV photolysis of the reaction mixtures. The evidence of •CH<inf>3</inf> radical formation in the pyrolytic decomposition of the reaction mixtures by exposure to ultrasound or in methane irradiated with microwave plasma have been reported previously. However, the pyrolytic •CH<inf>3</inf> radicals were not found in both plasma and H<inf>2</inf>O<inf>2</inf>-UV photolysis condition. These results suggests that free radicals produced by Ar-CAP are most likely due to the reaction between abundant •OH radicals and alcohol molecules.

DOI： 10.1088/1361-6463/aaa885

Facile fabrication of a poly(ethylene terephthalate) membrane filter with precise arrangement of through-holes 査読有り

Kihara, N; Odaka, H; Kuboyama, D; Onoshima, D; Ishikawa, K; Baba, Y; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 3 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Although membrane filters are indispensable in biochemical analysis fields, most methods for through-hole fabrication are complex and inefficient. We developed a simple method of fabricating poly(ethylene terephthalate) (PET) membrane filters with a precise arrangement of through-holes for the isolation of circulating tumor cells (CTCs) based on their size. By photolithography and dry etching, highly packed 380,000 through-holes with a diameter of 7 μm were able to cover a whole area with a diameter of 13 mm. Device fabrication for the size-based capture of rare cells in blood such as CTCs is realized in this study.

DOI： 10.7567/JJAP.57.037001

Reduced HeLa cell viability in methionine-containing cell culture medium irradiated with microwave-excited atmospheric-pressure plasma 査読有り

Takahashi, Y; Taki, Y; Takeda, K; Hashizume, H; Tanaka, H; Ishikawa, K; Hori, M

PLASMA PROCESSES AND POLYMERS 15 巻 ( 3 ) 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

The mechanism underlying the death of cancer cells incubated in plasma-activated medium (PAM) prepared by irradiation of culture medium with atmospheric-pressure plasma is revealed by analyzing changes in the culture medium composition using liquid chromatography-tandem mass spectrometry and nuclear magnetic resonance spectroscopy. The concentration of the essential amino acid methionine declined in microwave-excited plasma-irradiated medium, whereas, that of methionine sulfoxide increased due to oxidation of methionine. The decrease in methionine concentration in the cell culture medium rather than the increase in methionine sulfoxide leads to the decline in the survival rate of HeLa cells incubated in PAM. These results provide useful insights into the mechanism of selective cancer cell death in PAM.

DOI： 10.1002/ppap.201700200

Nanographene synthesis employing in-liquid plasmas with alcohols or hydrocarbons 査読有り

Ando, A; Ishikawa, K; Kondo, H; Tsutsumi, T; Takeda, K; Ohta, T; Ito, M; Hiramatsu, M; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 2 ) 2018年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Graphenes of nanometer-scale grain size (nanographenes) were synthesized using in-liquid plasmas with alcohols or hydrocarbons. This method of nanographene synthesis showed a trade-off relationship between crystallinity and synthesis rate. The high crystallinity of nanographenes synthesized with alcohols was evaluated from the small full width at half maxima (FWHM) of the G band in Raman scattering spectra. On the other hand, in the case of using hydrocarbons such as n-hexane and benzene, a significantly high synthesis rate was obtained but the crystallinity of nanographenes was low. It was found that hydroxyl groups and oxygen atoms of liquid sources play important roles in determining the crystallinity of synthesized nanographenes.

DOI： 10.7567/JJAP.57.026201

Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials FOREWORD 査読有り Open Access

Naritsuka, S; Miyazaki, S; Fujiwara, Y; Hiramatsu, M; Inoue, Y; Ishikawa, K; Ito, M; Itoh, T; Kasu, M; Miyake, H; Sasaki, M; Shirafuji, T; Suda, Y

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 1 ) 2018年1月

Electron impact ionization of perfluoro-methyl-vinyl-ether C3F6O 査読有り

Kondo, Y; Ishikawa, K; Hayashi, T; Sekine, M; Hori, M

PLASMA SOURCES SCIENCE & TECHNOLOGY 27 巻 ( 1 ) 2018年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Sources Science and Technology

A mechanism for the electron impact ionization of perfluoro-methyl-vinyl-ether (CF<inf>3</inf>OCF=CF<inf>2</inf>) molecules was studied theoretically using quantum chemical calculations. Positive and negative C<inf>2</inf>F<inf>3</inf>O- ions were abundantly generated, as supported by quadrupole mass spectrometry observations. The vinyl ethers easily dissociated at the ether bond due to polarization of the charge on the bridging oxygen atom. Consequently, perfluoro-vinyl-ethers form abundant ions via ether-specific pathways.

DOI： 10.1088/1361-6595/aaa22e

Plasma-activated medium (PAM) kills human cancer-initiating cells 査読有り Open Access

Ikeda, J; Tanaka, H; Ishikawa, K; Sakakita, H; Ikehara, Y; Hori, M

PATHOLOGY INTERNATIONAL 68 巻 ( 1 ) 頁： 23 - 30 2018年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Pathology International

Medical non-thermal plasma (NTP) treatments for various types of cancers have been reported. Cells with tumorigenic potential (cancer-initiating cells; CICs) are few in number in many types of tumors. CICs efficiently eliminate anti-cancer chemicals and exhibit high-level aldehyde dehydrogenase (ALDH) activity. We previously examined the effects of direct irradiation via NTP on cancer cells; even though we targeted CICs expressing high levels of ALDH, such treatment affected both non-CICs and CICs. Recent studies have shown that plasma-activated medium (PAM) (culture medium irradiated by NTP) selectively induces apoptotic death of cancer but not normal cells. Therefore, we explored the anti-cancer effects of PAM on CICs among endometrioid carcinoma and gastric cancer cells. PAM reduced the viability of cells expressing both low and high levels of ALDH. Combined PAM/cisplatin appeared to kill cancer cells more efficiently than did PAM or cisplatin alone. In a mouse tumor xenograft model, PAM exerted an anti-cancer effect on CICs. Thus, our results suggest that PAM effectively kills both non-CICs and CICs, as does NTP. Therefore, PAM may be a useful new anti-cancer therapy, targeting various cancer cells including CICs.

DOI： 10.1111/pin.12617

Selective production of reactive oxygen and nitrogen species in the plasma-treated water by using a nonthermal high-frequency plasma jet 査読有り

Uchida, G; Takenaka, K; Takeda, K; Ishikawa, K; Hori, M; Setsuhara, Y

JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 1 ) 2018年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

We present the control of H<inf>2</inf>O<inf>2</inf> and NO<inf>2</inf> - productions in deionized water by using a high-frequency plasma jet driven by a 60 MHz voltage. In the gas phase, the high-frequency plasma jet has a high O (3P) atom density of 8 × 1014 cm-3, which is two orders of magnitude higher than that of the low-frequency plasma jet driven by a 5 kHz voltage. Concerning the production of reactive oxygen and nitrogen species in the liquid phase, with the direct contact of the plasma jet to the liquid surface, the H<inf>2</inf>O<inf>2</inf> concentration is higher than the NO<inf>2</inf> - concentration. On the other hand, without the observable contact of the high-frequency plasm jet with high plasma density to the liquid surface, the NO<inf>2</inf> - concentration increases with the flow rate of N<inf>2</inf>(20%)O<inf>2</inf>(80%) gas added to the Ar discharge gas and becomes more dominant compared with H<inf>2</inf>O<inf>2</inf> in the plasma-treated water. H<inf>2</inf>O<inf>2</inf> and NO<inf>2</inf> - could be selectively produced in the plasma-treated water by using a nonthermal high-frequency plasma jet, which is a promising tool for biomedical applications.

DOI： 10.7567/JJAP.57.0102B4

Rapid growth of micron-sized graphene flakes using in-liquid plasma employing iron phthalocyanine-added ethanol 査読有り Open Access

Amano, T; Kondo, H; Ishikawa, K; Tsutsumi, T; Takeda, K; Hiramatsu, M; Sekine, M; Hori, M

APPLIED PHYSICS EXPRESS 11 巻 ( 1 ) 2018年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Giant graphene flakes on the micron scale were synthesized and grown in plasmas in liquid-phase pure ethanol with added iron phthalocyanine (FePc) in a solvent. At atmospheric pressure, plasmas were generated in the gas phase filled with Ar and in the liquid phases comprising bubbles and liquid solutions. In the mixture of FePc in ethanol, nanographene sheets aggregated to form giant graphene flakes, as confirmed by the D, G, and 2D bands in the corresponding Raman spectra. Therefore, a bottom-up approach of graphite synthesis from pure ethanol with additives and a catalyst was realized by in-liquid plasma processing.

DOI： 10.7567/APEX.11.015102

Cell Deposition Microchip with Micropipette Control over Liquid Interface Motion. 査読有り

Onoshima D, Hattori Y, Yukawa H, Ishikawa K, Hori M, Baba Y

Cell medicine 10 巻頁： 2155179017733152 2018年

Isotropic atomic level etching of tungsten using formation and desorption of tungsten fluoride 査読有り

Shinoda, K; Miyoshi, N; Kobayashi, H; Hanaoka, Y; Kawamura, K; Izawa, M; Ishikawa, K; Hori, M

ADVANCED ETCH TECHNOLOGY FOR NANOPATTERNING VII 10589 巻 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of SPIE the International Society for Optical Engineering

A selective, rapid thermal-cyclic atomic-level etching (ALE) of tungsten is developed. The first step of this process is exposing the surface of tungsten with hydrofluorocarbon plasma at -22°C to form a tungsten fluoride-based surface modified layer on the tungsten surface. The second step is rapid thermal annealing with infrared (IR) irradiation to remove the surface modified layer. Tungsten 4f peaks and a fluorine 1s peak, which were assigned to tungsten fluoride, were observed by in-situ x-ray photoelectron spectroscopy immediately after plasma exposure. The peaks that originated from tungsten fluoride disappeared after the samples were annealed. Cyclic etching tests were carried out by repeating plasma exposure and IR irradiation with a 300-mm ALE tool. Films of tungsten, TiN, and SiO<inf>2</inf> were used as sample materials. The amount of etched tungsten increased as the number of cycle repetitions increased. The etched amount per cycle for tungsten was 0.8 nm. In comparison, etching of TiN and SiO<inf>2</inf> was not detected. Conformal etching profiles of patterned samples after 60 cycles were obtained. Furthermore, the etched amount per cycle showed saturation behavior with regard to plasma exposure time. Selective, rapid thermal cyclic ALE of tungsten was thus successfully demonstrated.

DOI： 10.1117/12.2297241

Glioblastoma Cell Lines Display Different Sensitivities to Plasma-Activated Medium 査読有り

Tanaka H., Mizuno M., Ishikawa K., Takeda K., Hashizume H., Nakamura K., Utsumi F., Kajiyama H., Okazaki Y., Toyokuni S., Akiyama S., Maruyama S., Kikkawa F., Hori M.

IEEE Transactions on Radiation and Plasma Medical Sciences 2 巻 ( 2 ) 頁： 99 - 102 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE Transactions on Radiation and Plasma Medical Sciences

Plasma-activated medium (PAM) is a novel chemotherapy that induces reactive oxygen species (ROS) and cell death in a wide range of cancer cell types, suggesting that PAM may be a promising therapeutic option for cancer treatment. However, dose response experiments suggest that PAM sensitivity is cell line specific. We examined the sensitivities of three glioblastoma cell lines to PAM, and found a wide variation in cell killing that was linked to differences in PAM induced ROS and apoptosis. These results indicate that the PAM sensitivity of glioblastoma cells, and potentially cancer cells more generally, is heterogeneous and likely to be dependent on the regulation of apoptosis and antioxidant pathways in target cells.

DOI： 10.1109/trpms.2017.2721973

Oncogene mutation analysis of circulating tumor cells using single-cell membrane separation and DNA amplification 査読有り

Onoshima D., Kuboyama D., Kihara N., Tanaka H., Hase T., Yukawa H., Ishikawa K., Odaka H., Hasegawa Y., Hori M., Baba Y.

22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2018 3 巻頁： 1291 - 1293 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2018

We present a study of genomic profiling for circulating tumor cells (CTCs) using a blood microfiltration system. DNA amplification of CTCs was performed with a microfilter for single cancer cells in a clinical setting. This strategy was successfully used to detect the driver mutations in epidermal growth factor (EGF) receptor oncogenes by quantitative PCR and characterize the dosing effect of molecularly targeted drug for lung cancer.

Exosome isolation toward cancer diagnosis using glass filter with nanoporous structure 査読有り Open Access

Aoki K., Yukawa H., Onoshima D., Yamazaki S., Kihara N., Koguchi R., Takahashi K., Odaka H., Ishikawa K., Hori M., Baba Y.

22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2018 3 巻頁： 1409 - 1410 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：22nd International Conference on Miniaturized Systems for Chemistry and Life Sciences Microtas 2018

We present a study of centrifugal filtration device toward easy-to-use approach of non-invasive liquid biopsy for cancer diagnosis by cell-derived nanoscale vesicles (exosomes). A phase-dispersed glass filter having nanoporous structure was embedded into a spin column to trap exosomes with small centrifuge. This device enabled over 90% exosome isolation from biological samples within 10 minutes.

DOI： 10.1088/1361-6595/ac12bf

Dynamic analysis of reactive oxygen nitrogen species in plasma-activated culture medium by UV absorption spectroscopy 査読有り国際共著

Brubaker, TR; Ishikawa, K; Takeda, K; Oh, JS; Kondo, H; Hashizume, H; Tanaka, H; Knecht, SD; Bilén, SG; Hori, M

JOURNAL OF APPLIED PHYSICS 122 巻 ( 21 ) 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

The liquid-phase chemical kinetics of a cell culture basal medium during treatment by an argon-fed, non-equilibrium atmospheric-pressure plasma source were investigated using real-time ultraviolet absorption spectroscopy and colorimetric assays. Depth- and time-resolved NO2- and NO3- concentrations were strongly inhomogeneous and primarily driven by convection during and after plasma-liquid interactions. H<inf>2</inf>O<inf>2</inf> concentrations determined from deconvolved optical depth spectra were found to compensate for the optical depth spectra of excluded reactive species and changes in dissolved gas content. Plasma-activated media remained weakly basic due to NaHCO<inf>3</inf> buffering, preventing the H+-catalyzed decomposition of NO2- seen in acidic plasma-activated water. An initial increase in pH may indicate CO<inf>2</inf> sparging. Furthermore, the pH-dependency of UV optical depth spectra illustrated the need for pH compensation in the fitting of optical depth data.

DOI： 10.1063/1.4999256

Dependence of absolute photon flux on infrared absorbance alteration and surface roughness on photoresist polymers irradiated with vacuum ultraviolet photons emitted from HBr plasma 査読有り

Zhang, Y; Takeuchi, T; Ishikawa, K; Hayashi, T; Takeda, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 12 ) 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The absolute fluxes of vacuum ultraviolet (VUV) photons emitted from HBr plasma were analyzed and the effects of VUV photons on a photoresist polymer in ArF-excimer-laser (193 nm) lithography were quantitatively investigated on the basis of the infrared spectra attributed to the C=O region. The spectral peak intensity assigned to the methacrylic acid (MAA) in the photoresist drastically decreased owing to the loss of this monomer caused by the irradiation of VUV photons at dosages below 16 - 1016 photons/cm2. X-ray photoelectron spectroscopy observation showed that the removed monomer moved to the surface and generated volatile products that induced a decrease in film thickness. As a consequence, the surface became rough during the early-stage irradiation at dosages lower than 16 - 1016 photons/cm2 owing to the monomer loss of MAA with volatile product formation and subsequent cross-linking reactions.

DOI： 10.7567/JJAP.56.126503

State of the art in medical applications using non-thermal atmospheric pressure plasma 査読有り国際共著

Tanaka H., Ishikawa K., Mizuno M., Toyokuni S., Kajiyama H., Kikkawa F., Metelmann H.R., Hori M.

Reviews of Modern Plasma Physics 1 巻 ( 1 ) 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Reviews of Modern Plasma Physics

Plasma medical science is a novel interdisciplinary field that combines studies on plasma science and medical science, with the anticipation that understanding the scientific principles governing plasma medical science will lead to innovations in the field. Non-thermal atmospheric pressure plasma has been used for medical treatments, such as for cancer, blood coagulation, and wound healing. The interactions that occur between plasma and cells/tissues have been analyzed extensively. Direct and indirect treatment of cells with plasma has broadened the applications of non-thermal atmospheric pressure plasma in medicine. Examples of indirect treatment include plasma-assisted immune-therapy and plasma-activated medium. Controlling intracellular redox balance may be key in plasma cancer treatment. Animal studies are required to test the effectiveness and safety of these treatments for future clinical applications.

DOI： 10.1007/s41614-017-0004-3

Intracellular responses to reactive oxygen and nitrogen species, and lipid peroxidation in apoptotic cells cultivated in plasma-activated medium 査読有り

Furuta, R; Kurake, N; Ishikawa, K; Takeda, K; Hashizume, H; Tanaka, H; Kondo, H; Sekine, M; Hori, M

PLASMA PROCESSES AND POLYMERS 14 巻 ( 11 ) 2017年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plasma Processes and Polymers

A mechanism of the cytotoxicity of plasma-activated medium (PAM) is revealed by examining the intracellular effects of reactive oxygen nitrogen species (RONS) and lipid oxidation. PAM is cell culture medium activated by irradiation using non-equilibrium atmospheric-pressure plasma using pure Ar gas in ambient air. Extracellular RONS in PAM induced the apoptotic death of HeLa cells. Temporal changes in intracellular RONS, such as ONOO−, NO, and (Formula presented.), were analyzed. Intracellular RONS generation in HeLa cells following incubation in PAM triggered activation of the caspase cascade pathway and lipid peroxidation of intracellular membranes to induce apoptosis.

DOI： 10.1002/ppap.201700123

Surface roughening of photoresist after change of the photon/radical and ion treatment sequence 査読有り

Zhang, Y; Takeuchi, T; Ishikawa, K; Takeda, K; Kondo, H; Sekine, M; Hori, M

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 35 巻 ( 6 ) 2017年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Vacuum Science and Technology A Vacuum Surfaces and Films

The formation of surface roughness during ion irradiation was suppressed by photon/radical pretreatment of a photoresist with HBr or H<inf>2</inf> plasmas. The opposite sequence of treatment after ion irradiation enhanced the surface roughness. The enhancement of roughness after post-treatment was not correlated with a decrease in the film thickness, reactions of Br radicals at the surface, or with the presence of the amorphous carbon-like layer generated by ion irradiation because similar modification was observed for the pretreatment. Fourier transform infrared spectroscopy analysis revealed that the intensities of peaks originated from the C=O absorption of methacrylic acid and methacrylate groups were decreased by irradiation with vacuum ultraviolet light at wavelengths in the range between 115 and 170 nm emitted from HBr or H<inf>2</inf> plasmas. The removal of the C=O groups possibly generated dangling bonds and induced crosslinking reactions of the photoresist polymers. The nonuniformity of crosslinking reactions on the roughened photoresist intensively increased the surface roughness.

DOI： 10.1116/1.4994218

Crystallization of calcium oxalate dihydrate in a buffered calcium-containing glucose solution by irradiation with non-equilibrium atmospheric pressure plasma 査読有り

最先端プラズマバイオ技術招待有り査読有り Open Access

堀勝，石川健治，近藤隆，田中宏昌，橋爪博司

放射線化学頁： 3 - 14 2017年10月

Kurake, N; Tanaka, H; Ishikawa, K; Nakamura, K; Kajiyama, H; Kikkawa, F; Mizuno, M; Ikehara, Y; Hori, M

JOURNAL OF APPLIED PHYSICS 122 巻 ( 14 ) 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

Oxalate was synthesized in the glucose solution by irradiation with non-equilibrium atmospheric pressure plasma (NEAPP), in which the NEAPP plume contacted the solution surface, via the generation of several intermediate organic products such as gluconic acid. A thermodynamically unstable phase of calcium oxalate dihydrate crystallized rapidly during incubation of a NEAPP-irradiated glucose solution that contained calcium ions and was buffered at neutral pH. Longer irradiation times increased the growth rate and the number of seed crystals.

DOI： 10.1063/1.5006598

High-durability catalytic electrode composed of Pt nanoparticle-supported carbon nanowalls synthesized by radical-injection plasma-enhanced chemical vapor deposition 査読有り

Imai, S; Kondo, H; Cho, H; Kano, H; Ishikawa, K; Sekine, M; Hiramatsu, M; Ito, M; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 巻 ( 40 ) 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

For polymer electrolyte fuel cell applications, carbon nanowalls (CNWs) were synthesized by radical-injection plasma-enhanced chemical vapor deposition, and a high density of Pt nanoparticles (>1012 cm-2) was supported on the CNWs using a supercritical fluid deposition system. The high potential cycle tests were applied and the electrochemical surface area of the Pt nanoparticle-supported CNWs did not change significantly, even after 20 000 high potential cycles. According to transmission electron microscopy observations, the mean diameter of Pt changed slightly after the cycle tests, while the crystallinity of the CNWs evaluated using Raman spectroscopy showed almost no change.

DOI： 10.1088/1361-6463/aa8131

Lipid droplets exhaustion with caspases activation in HeLa cells cultured in plasma-activated medium observed by multiplex coherent anti-Stokes Raman scattering microscopy 査読有り

Cold atmospheric helium plasma causes synergistic enhancement in cell death with hyperthermia and an additive enhancement with radiation 査読有り Open Access

Moniruzzaman, R; Rehman, MU; Zhao, QL; Jawaid, P; Takeda, K; Ishikawa, K; Hori, M; Tomihara, K; Noguchi, K; Kondo, T; Noguchi, M

SCIENTIFIC REPORTS 7 巻 ( 1 ) 頁： 11659 2017年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Cold atmospheric plasmas (CAPs) have been proposed as a novel therapeutic method for its anti-cancer potential. However, its biological effects in combination with other physical modalities remain elusive. Therefore, this study examined the effects of cold atmospheric helium plasma (He-CAP) in combination with hyperthermia (HT) 42 °C or radiation 5 Gy. Synergistic enhancement in the cell death with HT and an additive enhancement with radiation were observed following He-CAP treatment. The synergistic effects were accompanied by increased intracellular reactive oxygen species (ROS) production. Hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>) and superoxide (O<inf>2</inf> •-) generation was increased immediately after He-CAP treatment, but fails to initiate cell death process. Interestingly, at late hour's He-CAP-induced O<inf>2</inf> •- generation subsides, however the combined treatment showed sustained increased intracellular O<inf>2</inf> •- level, and enhanced cell death than either treatment alone. He-CAP caused marked induction of ROS in the aqueous medium, but He-CAP-induced ROS seems insufficient or not completely incorporated intra-cellularly to activate cell death machinery. The observed synergistic effects were due to the HT effects on membrane fluidity which facilitate the incorporation of He-CAP-induced ROS into the cells, thus results in the enhanced cancer cell death following combined treatment. These findings would be helpful when establishing a therapeutic strategy for CAP in combination with HT or radiation.

DOI： 10.1038/s41598-017-11877-8

Furuta, R; Kurake, N; Takeda, K; Ishikawa, K; Ohta, T; Ito, M; Hashizume, H; Tanaka, H; Kondo, H; Sekine, M; Hori, M

BIOINTERPHASES 12 巻 ( 3 ) 頁： 031006 2017年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Biointerphases

The multiplex coherent anti-Stokes Raman scattering microscopy allowed label-free visualization of cytoplasmic lipid droplets (LDs). The LDs, which act to conserve energy storage, are usually accumulated during the normal apoptosis of HeLa cells with activation of caspase-3/7 leading to downregulation of the fatty acid catabolism pathways. During cultivating in nonthermal plasmaactivated medium (PAM), while the activation of caspase-3/7 was induced, the authors found that a dynamic exhaustion of the intracellular LDs, underlying the metabolic mechanism of the PAMinduced apoptotic cell death of HeLa cells.

DOI： 10.1116/1.4997170

高温での窒化ガリウム低損傷塩素エッチング査読有り

石川健治, 劉沢成, 今村真人, 堤隆嘉, 小田修, 近藤博基, 関根誠, 堀勝

応用物理学会学術講演会講演予稿集 2017.2 巻 ( 0 ) 頁： 1758 - 1758 2017年8月

Laser diagnostics of properties of atmospheric pressure plasmas 査読有り

Ishikawa Kenji, Lin YuChun, Ando Atsushi, Wang Meng-Jiy, Hori Masaru

JSAP Annual Meetings Extended Abstracts 2017.2 巻 ( 0 ) 頁： 1701 - 1701 2017年8月

Reduction of chlorine radical chemical etching of GaN under simultaneous plasma-emitted photon irradiation 査読有り Open Access

Liu, ZC; Imamura, M; Asano, A; Ishikawa, K; Takeda, K; Kondo, H; Oda, O; Sekine, M; Hori, M

APPLIED PHYSICS EXPRESS 10 巻 ( 8 ) 2017年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Surface chemical reactions on the GaN surface with Cl radicals are thermally enhanced in the high-temperature Cl<inf>2</inf> plasma etching of GaN, resulting in the formation of etch pits and thereby, a roughened surface. Simultaneous irradiation of ultraviolet (UV) photons in Cl<inf>2</inf> plasma emissions with wavelengths of 258 and 306nm reduces the surface chemical reactions because of the photodissociation of both Ga and N chlorides, which leads to a suppression of the increase in surface roughness. Compared with Si-related materials, we point out that photon-induced reactions should be taken into account during the plasma processing of wide-bandgap semiconductors.

DOI： 10.7567/APEX.10.086502

Temperature dependence of protection layer formation on organic trench sidewall in H2/N2 plasma etching with control of substrate temperature 査読有り

Fukunaga, Y; Tsutsumi, T; Takeda, K; Kondo, H; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 7 ) 2017年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

For the etching of organic films in H2/N2 plasma, etched profiles are significantly determined by substrate temperature. Here, we control the substrate temperature variation within 3 °C during processing by modulating the plasma-discharge time. The evolution of the cross-sectional profile of line-and-space patterns was observed every 10s. At 60 and 100 °C, sidewall etching was observed during overetching, but not at 20 °C. During the main etching, the sidewalls were protected by the adsorption of by-products at various temperatures. Moreover, we investigated the temperature dependence of protection layer formation by analyzing the surface components of the organic film. The CN layer formed by N radicals has a protective effect that depends on the components of the CN layer. It was found that the ratio of C-N sp3 to C-N sp2 in the sidewall was highest at 100°C. By evaluating the radical contribution to CN layer formation, C-N sp3 bonds were observed to be formed by ions and radiation-assisted reaction.

DOI： 10.7567/JJAP.56.076202

Intracellular-molecular changes in plasma-irradiated budding yeast cells studied using multiplex coherent anti-Stokes Raman scattering microscopy 査読有り Open Access

Furuta, R; Kurake, N; Ishikawa, K; Takeda, K; Hashizume, H; Kondo, H; Ohta, T; Ito, M; Sekine, M; Hori, M

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 巻 ( 21 ) 頁： 13438 - 13442 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Chemistry Chemical Physics

Interactions between non-equilibrium atmospheric-pressure plasma (NEAPP) and living cells were examined using multiplex coherent anti-Stokes Raman scattering (CARS) microscopy. Our multiplex CARS analyses revealed that NEAPP irradiation generates short-lived radicals that induce a decrease in the mitochondrial activity of budding yeast cells.

DOI： 10.1039/c7cp00489c

Dry Process FOREWORD 査読有り

Ishikawa, K; Kinoshita, K; Higashi, S; Ichiki, T; Karahashi, K; Kuboi, N

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 6 ) 2017年6月

Hydrogen peroxide sensor based on carbon nanowalls grown by plasma-enhanced chemical vapor deposition 査読有り

Tomatsu, M; Hiramatsu, M; Foord, JS; Kondo, H; Ishikawa, K; Sekine, M; Takeda, K; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 6 ) 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Fabrication of an electrochemical sensor for hydrogen peroxide (H<inf>2</inf>O<inf>4</inf>) detection was demonstrated. H<inf>4</inf>O<inf>2</inf> is a major messenger molecule in various redox-dependent cellular signaling transductions. Therefore, sensitive detection of H<inf>2</inf>O<inf>2</inf> is greatly important in health inspection and environmental protection. Carbon nanowalls (CNWs) are composed of few-layer graphenes standing almost vertically on a substrate forming a three-dimensional structure. In this work, CNWs were used as a platform for H<inf>2</inf>O<inf>2</inf> sensing, which is based on the large surface area of conducting carbon and surface decoration with platinum (Pt) nanoparticles (NPs). CNWs were grown on carbon fiber paper (CFP) by inductively coupled plasma-enhanced chemical vapor deposition to increase the surface area. Then, the CNW surface was decorated with Pt-NPs by the reduction of H<inf>2</inf>PtCl<inf>6</inf>. Cyclic voltammetry results indicate that the Pt-decorated CNW/CFP electrode possesses excellent electrocatalytic activity for the reduction of H<inf>2</inf>O<inf>2</inf>. Amperometric responses indicate the high-sensitivity detection capability of the Pt-decorated CNW/CFP electrode for H<inf>2</inf>O<inf>2</inf>.

DOI： 10.7567/JJAP.56.06HF03

Growth of InN films by radical-enhanced metal organic chemical vapor deposition at a low temperature of 200 °C 査読有り

Takai, S; Lu, Y; Oda, O; Takeda, K; Kondo, H; Ishikawa, K; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 6 ) 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The InN films were deposited on GaN surfaces at a low temperature of 200 °C by radical-enhanced metal organic chemical vapor deposition (REMOCVD). The REMOCVD system can provide N radicals from the plasma of a N<inf>2</inf>-H<inf>2</inf> mixture gas without using ammonia. Two types of GaN substrate, bulk GaN and GaN on Si(111), were used. The growth mode was modeled as a step flow on the basis of surface morphology observation by atomic force microscopy.

DOI： 10.7567/JJAP.56.06HE08

Electron behaviors in afterglow of synchronized dc-imposed pulsed fluorocarbon-based plasmas 査読有り

Ueyama, T; Fukunaga, Y; Tsutsumi, T; Takeda, K; Kondo, H; Ishikawa, K; Sekine, M; Iwata, M; Ohya, Y; Sugai, H; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 6 ) 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Electron behaviors in a pulsed dual radio frequency (RF) capacitively coupled plasma of a mixture of C<inf>4</inf>F<inf>8</inf>, O<inf>2</inf>, and Ar gases, where the DC bias of %300V in the RF-on period was imposed and synchronously increased to %1000V in the RF-off period, were investigated. The synchronous DC bias prolongs the electron density (n<inf>e</inf>) decay and provides emission of Ar at a wavelength of 750.38nm in early afterglow at 3 μs during the RF-off period of 10 kHz pulse modulation. The rapid n<inf>e</inf> decay occurred with the electron attachments to the electronegative fluorocarbons, and thus the plasma consisting of positive and negative ions was generated. The DC bias voltage seems to be applied between the electrodes and the positive ions accelerated to the top electrode, and enhanced the secondary electron generation at the top electrode surface in the RF-off period with the ion bombardments, concomitantly with the synchronous emissions.

DOI： 10.7567/JJAP.56.06HC03

Progress and prospects in nanoscale dry processes: How can we control atomic layer reactions? 査読有り国際共著 Open Access

Ishikawa, K; Karahashi, K; Ichiki, T; Chang, JP; George, SM; Kessels, WMM; Lee, HJ; Tinck, S; Um, JH; Kinoshita, K

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 6 ) 2017年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

In this review, we discuss the progress of emerging dry processes for nanoscale fabrication. Experts in the fields of plasma processing have contributed to addressing the increasingly challenging demands in achieving atomic-level control of material selectivity and physicochemical reactions involving ion bombardment. The discussion encompasses major challenges shared across the plasma science and technology community. Focus is placed on advances in the development of fabrication technologies for emerging materials, especially metallic and intermetallic compounds and multiferroic, and two-dimensional (2D) materials, as well as state-of-the-art techniques used in nanoscale semiconductor manufacturing with a brief summary of future challenges.

DOI： 10.7567/JJAP.56.06HA02

Selective atomic-level etching using two heating procedures, infrared irradiation and ion bombardment, for next-generation semiconductor device manufacturing 査読有り

Shinoda, K; Miyoshi, N; Kobayashi, H; Miura, M; Kurihara, M; Maeda, K; Negishi, N; Sonoda, Y; Tanaka, M; Yasui, N; Izawa, M; Ishii, Y; Okuma, K; Saldana, T; Manos, J; Ishikawa, K; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 巻 ( 19 ) 2017年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

The demand for precisely controlled etching is increasing as semiconductor device geometries continue to shrink. To fulfill this demand, cyclic atomic level/layer etching will become one of the key technologies in semiconductor device manufacturing at nanometer dimensions. This review describes recent trends in semiconductor devices and some of the latest results on cyclic atomic-level etching. In particular, it focuses on two types of cyclic etching that use different heating procedures: infrared irradiation for isotropic etching and Ar+ ion bombardment for anisotropic etching. It describes how an inductively-coupled-plasma down-flow etching apparatus with infrared lamps can be used for isotropic cyclic etching. The isotropic cyclic etching of SiN involves the formation and thermal desorption of ammonium hexafluorosilicate-based surface modified layers. This method features high selectivity with respect to SiO<inf>2</inf>, atomic-level control of the amount of SiN etching, and isotropic etched features. On the other hand, the anisotropic cyclic etching with Ar+ ion bombardment uses a microwave electron-cyclotron-resonance plasma etching apparatus. The anisotropic process for poly Si is composed of cyclic repetitions of chlorine adsorption and Ar+ ion bombardment. The anisotropic process for SiN is composed of cyclic repetitions involving an adsorption step using hydrofluorocarbon chemistry and a desorption step using Ar+ ion bombardment. Potential applications of these isotropic/anisotropic cyclic etching processes are described.

DOI： 10.1088/1361-6463/aa6874

Spatial distributions of O, N, NO, OH and vacuum ultraviolet light along gas flow direction in an AC-excited atmospheric pressure Ar plasma jet generated in open air 査読有り

Takeda, K; Ishikawa, K; Tanaka, H; Sekine, M; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 巻 ( 19 ) 2017年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

Ground-state O (3P<inf>j</inf>) and N (4S°) atoms, nitric oxide (NO) and hydroxyl (OH) radicals, and vacuum ultraviolet (VUV) radiation emitted from an AC-excited Ar atmospheric pressure plasma jet (APPJ) operated in open air were measured using VUV absorption spectroscopy, laser induced fluorescence spectroscopy and optical emission spectroscopy, respectively. The O (3P<inf>j</inf>) density decreased with increasing distance from the plasma head, and the decrease rate in the edge region of the plasma jet around 8 mm distance was especially high. On the other hand, the N (4S°) atom density was almost constant up to approximately 10 mm and increased with the distance over 12 mm. The relative NO density increased with the distance up to 10 mm and then became saturated, although the OH density was significantly reduced from the plasma jet exit of the head, and could be observed in the plasma jet only up to the distance of 5 mm. Emissions due to N, H and O atoms were observed in the VUV region and the emission intensity for N atoms (wavelength: 174.3 nm) decreased exponentially with increasing the distance. The results obtained with the Ar APPJ operated in open air conditions indicate the generation of many different reactive oxygen and nitrogen species by gas-phase reactions, and the composition of the reactive species is strongly dependent on the distance from the plasma head. These results are very useful for clarifying the kinetics of reactive species in APPJs and their application in various technological fields.

DOI： 10.1088/1361-6463/aa6555

電子スピン共鳴法を活用したプラズマバイオ反応プロセスの診断招待有り査読有り

石川健治, 近藤隆, 竹田圭吾, 呉準席, 橋爪博司, 田中宏昌, 近藤博基, 太田貴之, 伊藤昌文, 関根誠, 堀勝

プラズマ核融合学会誌 2017年5月

Bactericidal pathway of Escherichia coli in buffered saline treated with oxygen radicals 査読有り

Kobayashi, T; Iwata, N; Oh, JS; Hahizume, H; Ohta, T; Takeda, K; Ishikawa, K; Hori, M; Ito, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 巻 ( 15 ) 2017年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

Bactericidal effects of phosphate buffered saline treated with electrically neutral oxygen radicals on Escherichia coli (E. coli) are studied using an atmospheric pressure radical source and colony counting method. To clarify the bactericidal mechanism, the chemistry in phosphate buffers treated with oxygen radicals with and without saline has been quantitatively investigated using the well-established chemical reporters N,N-diethyl-p-phenylenediamine reagent and Amplex Red for residual chlorine (HClO and ClO-) and hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>), respectively. From the results, we have found that the presence of chlorine in the solutions treated with oxygen radicals is the most important factor in the further chemical reactions to generate hypochlorous acid in E. coli death, and H<inf>2</inf>O<inf>2</inf> is also linked to the bactericidal effect via an indirect chemical pathway.

DOI： 10.1088/1361-6463/aa61d7

Effects of •OH and •NO radicals in the aqueous phase on H2O2 and NO2- generated in plasma-activated medium 査読有り

Kurake, N; Tanaka, H; Ishikawa, K; Takeda, K; Hashizume, H; Nakamura, K; Kajiyama, H; Kondo, T; Kikkawa, F; Mizuno, M; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 巻 ( 15 ) 2017年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

A plasma-activated medium (PAM), which means a cell-culture medium irradiated with cold atmospheric plasmas or non-equilibrium atmospheric pressure plasma (NEAPP), has shown strong antitumor effects on various kinds of cells such as gastric cancer cells, human lung adenocarcinoma cells, human breast cancer cells and so on. In order to clarify the mechanism, it is extremely important to investigate the behaviors of stable and unstable reactive oxygen nitrogen species in culture medium irradiated by NEAPP. The roles of hydroxyl radicals (•OH) and nitric oxide (•NO) were studied to understand the dominant synthetic pathways of H<inf>2</inf>O<inf>2</inf> and in culture medium irradiated with NEAPP. In the PAM, •OH in the aqueous phase was generated predominantly by photo-dissociation. However, most of the H<inf>2</inf>O<inf>2</inf> nor generated in the PAM did not originate from aqueous •OH and •NO. Pathways for the generation of H<inf>2</inf>O<inf>2</inf> and are suggested based on the high concentrations of intermediates generated at the gas/aqueous-phase interface following NEAPP irradiation. On the basis of these results, the reaction model of chemical species in the culture medium is proposed.

DOI： 10.1088/1361-6463/aa5f1d

Spatial profiles of interelectrode electron density in direct current superposed dual-frequency capacitively coupled plasmas 査読有り Open Access

Ohya, Y; Ishikawa, K; Komuro, T; Yamaguchi, T; Takeda, K; Kondo, H; Sekine, M; Hori, M

JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 巻 ( 15 ) 2017年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D Applied Physics

We present experimentally determined spatial profiles of the interelectrode electron density (n <inf>e</inf>) in dual-frequency capacitively coupled plasmas in which the negative direct current (dc) bias voltage (V <inf>dc</inf>) is superposed; in the experiment, 13 MHz (P <inf>low</inf>) was applied to the lower electrode and 60 MHz (P <inf>high</inf>) to the upper electrode. The bulk n <inf>e</inf> increased substantially with increases in the external power, P <inf>high</inf>, P <inf>low</inf>, and with increases in V <inf>dc</inf>. When P <inf>low</inf> was insufficient, the bulk n <inf>e</inf> decreased as the V <inf>dc</inf> bias increased. The bulk n <inf>e</inf> increased due to its dependence on V <inf>dc</inf>, especially for |V <inf>dc</inf>| > 500 V. This may correspond to the sheath voltages (V <inf>s</inf>) of the lower electrode. The n <inf>e</inf> values in front of the upper electrode were coupled with the V <inf>dc</inf>: the V <inf>dc</inf> dependence first decreased and then increased. The dc currents (I <inf>dc</inf>) of the upper electrode were collected when a large P <inf>low</inf> was applied. The value of I <inf>dc</inf> at the threshold value of V <inf>dc</inf> ≈ V <inf>s</inf> (e.g. -500 V) increased with an increase in n <inf>e</inf>. When |V <inf>dc</inf>| exceeded the threshold, the spatial n <inf>e</inf> profile and the I <inf>dc</inf> dependence were changed relative to the electrical characteristics of the dc superposition; this led to a change in the location of the maximum n <inf>e</inf>, the width of the area of n <inf>e</inf> depletion in front of the electrodes, and a transition in the electron heating modes.

DOI： 10.1088/1361-6463/aa60f7

酸素ラジカル照射された馬肉水抽出液のESR測定査読有り

北田悠人, 石川健治, 堀勝, 伊藤昌文, 林利哉

応用物理学会学術講演会講演予稿集 2017.1 巻 ( 0 ) 頁： 1802 - 1802 2017年3月

マルチプレックスCARSによるプラズマと細胞の相互作用の観察査読有り

古田凌, 堀勝, 関根誠, 石川健治, 太田貴之, 近藤博基, 橋爪博司, 竹田圭吾, 伊藤昌文, 田中宏昌

応用物理学会学術講演会講演予稿集 2017.1 巻 ( 0 ) 頁： 1801 - 1801 2017年3月

Behavior of absolute densities of atomic oxygen in the gas phase near an object surface in an AC-excited atmospheric pressure He plasma jet 査読有り Open Access

Takeda, K; Kumakura, T; Ishikawa, K; Tanaka, H; Sekine, M; Hori, M

APPLIED PHYSICS EXPRESS 10 巻 ( 3 ) 2017年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

The quantitative behavior of atomic oxygen in the gas phase near a Cu wire surface in an AC-excited atmospheric pressure He plasma jet in open air was measured using time-resolved vacuum ultraviolet absorption spectroscopy. The atomic oxygen density had a peak at a distance between the plasma source and the Cu wire, and the peak position moved away from the source with an increase in the gas flow rate. The behavior is considered to be dependent on the plasma density and the influence of ambient air. The results are important for supplying atomic oxygen to samples for plasma jet treatment in the atmosphere.

DOI： 10.7567/APEX.10.036201

Characteristics of optical emissions of arc plasma processing for high-rate synthesis of highly crystalline single-walled carbon nanotubes 査読有り

Ando, A; Takeda, K; Ohta, T; Ito, M; Hiramatsu, M; Ishikawa, K; Kondo, H; Sekine, M; Suzuki, T; Inoue, S; Ando, Y; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 3 ) 2017年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Single-walled carbon nanotubes (SWNTs) were synthesized with a high growth rate using an arc plasma employing carbon electrodes with a Ni-Y mixture catalyst. However, the mechanism of growth of highly crystalline SWNTs has not been clarified. Reactions between carbon and catalyst are considered to be one of the crucial factors in SWNT growth. Optical emission spectroscopy (OES) provides the information about the species in the plasma. C2, Ni, and Y emissions in the arc plasma at different currents were measured to investigate the relationship between active species in the arc plasma and the SWNTsynthesis. On the basis of OES results, it was found that the balance between catalytic metal atoms and C2 radical emissions indicated the crystallinity ratio of SWNTs in thin graphitic or amorphous carbon layers. These results are useful for controlling the growth of SWNTs employing arc plasmas.

DOI： 10.7567/JJAP.56.035101

Investigation of effects of ion energies on both plasma-induced damage and surface morphologies and optimization of high-temperature Cl2 plasma etching of GaN 査読有り

Liu, ZC; Pan, JL; Asano, A; Ishikawa, K; Takeda, K; Kondo, H; Oda, O; Sekine, M; Hori, M

JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 2 ) 2017年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

The minimization of plasma-induced damage (PID) in plasma etching is important for the precise and smooth removal of a depth of approximately 7 nm of GaN films to fabricate gate-recess GaN-based normally-off power electronic devices. We have systematically studied the photoluminescence (PL) properties and surface morphologies of GaN films exposed to Cl<inf>2</inf> plasma at 400°C, focusing on their dependences on etch time and ion energy. It is noticeable that PL degradation saturated at etch times of more than 2 min, while surface roughness increased continuously with etch time. Variations of surface roughness with bias voltage were negligible. PID was successfully suppressed by reducing bias voltage, leading to the decrease in incident ion energy on the surface, and thus the near-band-edge emission (NBE) intensity as a PL property was increased to 98.8% of the initial value.

DOI： 10.7567/JJAP.56.026502

Absolute density of precursor SiH3 radicals and H atoms in H2-diluted SiH4 gas plasma for deposition of microcrystalline silicon films 査読有り Open Access

Abe, Y; Ishikawa, K; Takeda, K; Tsutsumi, T; Fukushima, A; Kondo, H; Sekine, M; Hori, M

APPLIED PHYSICS LETTERS 110 巻 ( 4 ) 2017年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Letters

Microcrystalline hydrogenated silicon films were produced at a high deposition rate of about 2 nm/s by using a capacitively coupled plasma under a practical pressure of around 1 kPa. The SiH<inf>4</inf> source gas was almost fully dissociated when highly diluted with H<inf>2</inf> gas, and the dominant species in the gas phase were found to be SiH<inf>3</inf> radicals, which are film-growth precursors, and H atoms. The absolute density of these species was measured as the partial pressure of SiH<inf>4</inf> gas was varied. With the increasing SiH<inf>4</inf> gas flow rate, the SiH<inf>3</inf> radical density, which was on the order of 1012 cm-3, increased linearly, while the H-atom density remained constant at about 1012 cm-3. The film growth mechanism was described in terms of precursors, based on the measured flux of SiH<inf>3</inf> radicals and H atoms, and the relative fraction of higher-order radicals.

DOI： 10.1063/1.4974821

Thermally enhanced formation of photon-induced damage on GaN films in Cl2 plasma 査読有り

Liu Z., Asano A., Imamura M., Ishikawa K., Takeda K., Kondo H., Oda O., Sekine M., Hori M.

Japanese Journal of Applied Physics 56 巻 ( 9 ) 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Deep ultraviolet (UV) photons emitted from Cl<inf>2</inf> plasmas become a critical cause of degradation in both photoluminescence (PL) properties and surface stoichiometry as a result of plasma-induced damage on GaN films in Cl<inf>2</inf> plasma etching at high temperatures. The damages were formed thermally by photon-irradiations of plasma UV emissions with wavelengths of >258-306 nm from Cl<inf>2</inf> plasma at temperatures greater than 500 °C. The damage were observed with a depth of approximately 3.2 nm. The PL property degraded by the UV emission-induced damage at an early period of plasma etching and reached a constant value.

DOI： 10.7567/JJAP.56.096501

Thermal Cyclic Atomic-Level Etching of Nitride Films: A Novel Way for Atomic-Scale Nanofabrication 査読有り

Shinoda, K; Miyoshi, N; Kobayashi, H; Kurihara, M; Izawa, M; Ishikawa, K; Hori, M

ATOMIC LAYER DEPOSITION APPLICATIONS 13 80 巻 ( 3 ) 頁： 3 - 14 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ecs Transactions

A highly selective, rapid thermal-cyclic atomic-level etching (ALE) process for SiNx films has been developed. The first step of this process is exposing SiNx to hydrofluorocarbon plasma to form an (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> layer on the SiNx surface. The second step is rapid thermal annealing with infrared (IR) irradiation to decompose and sublimate the (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> layer. Etching of SiNx was observed after the (NH<inf>4</inf>)<inf>2</inf>SiF<inf>6</inf> layer was removed by thermal annealing. Cyclic etching tests were carried out by repeated plasma exposure and IR irradiation. It was found that the cyclic process is self-limiting because etching depth depends only on the cycle number and not on the plasma exposure time. A high selectivity over SiC<inf>2</inf> and poly Si was confirmed. This paper reviews the novel isotropic ALE for nitride films focusing on the surface reaction mechanism investigated by x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). Isotropic ALE of TiN was also demonstrated using the same approach.

DOI： 10.1149/08003.0003ecst