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

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

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

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

PubMed

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

PubMed

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