Faculty Profiles - ISHIKAWA, Kenji

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

Elaborate Cooperation of Poly(rC)-binding Proteins 1/2 and Glutathione in Ferroptosis Induced by Plasma-activated Ringer' s Lactate Reviewed Open Access

Li Jiang, Hao Zheng, Moe Ishida, Qinying Lyu, Shinya Akatsuka, Yashiro Motooka, Kotaro Sato, Yoshitaka Sekido, Kae Nakamura, Hiromasa Tanaka, Kenji Ishikawa, Hiroaki Kajiyama, Masaaki Mizuno, Masaru Hori, and Shinya Toyokuni

Free Radical Biology and Medicine Vol. 214 page： 28 - 41 2024.2

Surface sulfurization of amorphous carbon films in the chemistry of oxygen plasma added with SO2 or OCS for high-aspect-ratio etching Reviewed Open Access

Kenji Ishikawa, Thi-Thuy-Nga Nguyen, Yuta Aoki, Hiroyasu Sato, Junichi Kawakami, Shuji Tsuno, Shin-Nan Hsiao, and Masaru Hori

Applied Surface Science Vol. 645 page： 158876 2024.2

Oxygen radical irradiation transforms an organic fertilizer l-tryptophan into an environment and human-friendly bactericide Reviewed Open Access

Naoyuki Iwata, Kenji Ishikawa, Yasuhiro Nishikawa, Hiroyuki Kato, Motoyuki Shimizu, Masashi Kato, Hiromasa Tanaka, Masafumi Ito, and Masaru Hori

Environmental Technology and Innovation Vol. 33 page： 103496 2024.2

Seiko Nakagawa, Akinari Yokoya, Maki Ohara, Noriko Usami, Mizue Asada, Motoyasu Fujiwara, Toshikazu Nakamura, and Kenji Ishikawa

Radiation Physics and Chemistry Vol. 214 page： 111304 2024.1

Cold Atmospheric Pressure Plasma-Activated Liquids for Cancer Treatment Reviewed

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 Vol. 111 page： 150 - 162 2024

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

Taito Yoshie, Kenji Ishikawa, Thi-Thuy-Nga Nguyen, Shih-Nan Hsiao, Takayoshi Tsutsumi, Makoto Sekine, and Masaru Hori

Applied Surface Science Vol. 638 page： 157981 2023.11

Shih-Nan Hsiao, Makoto Sekine, Kenji Ishikawa, Yuki Iijima, Yoshinobu Ohya, and Masaru Hori

Applied Physics Letters Vol. 123 ( 21 ) page： 1 - 4 2023.11

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) Reviewed

Arun Kumar Dhasiyan, Swathy Jayaprasad, Frank Wilson Amalraj, Naohiro Shimizu, Osamu Oda, Kenji Ishikawa, and Masaru Hori

Japanese Journal of Applied Physics Vol. 62 ( SN ) page： SN1019 2023.11

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

Ma. Shanlene D.C. Dela Vega, Thi-Thuy-Nga Nguyen, Hiroki Kondo, Takayoshi Tsutsumi, Kenji Ishikawa, and Masaru Hori

Plasma Processes and Polymers Vol. 20 ( 11 ) page： 1 - 5 2023.11

The Possibility of Cancer Therapy with a Combination of Low-temperature Plasma and Hyperthermia Invited Reviewed

KONDO TAKASHI, HASHIZUME HIROSHI, TANAKA HIROMASA, ISHIKAWA KENJI, SAITOH JUN-ICHI, HORI MASARU

Thermal Medicine Vol. 39 ( 3 ) page： 21 - 30 2023.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Society for Thermal Medicine

Low temperature plasma (LTP) has been proposed as a novel therapeutic method for its anti-cancer potential. However, its biological effects in combination with other physical modalities remain to be elusive. Therefore, this study was aimed to determine the effects of low temperature helium plasma (He-LTP) in combination with mild hyperthermia (HT, 42℃ for 20 min). Human lymphoma U937 cells were exposed to HT, immediately after He-LTP treatment. He-LTP in combination with HT showed enhanced cell death, which was accompanied by increased intracellular reactive oxygen species (ROS) production. These findings suggest that He-LTP can enhance the apoptotic effects of mild HT due to the increased in intracellular ROS generation as He-LTP has been known to caused marked induction of ROS in the aqueous medium. These findings would be helpful when establishing a therapeutic strategy for LTP in combination with mild HT. Here, the biological effects of LTP, and the combination with hyperthermia and LTP or LTP -activated solutions for cancer therapy have been summarized in this review.

DOI： 10.3191/thermalmed.39.21

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

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

Japanese Journal of Applied Physics Vol. 62 ( SL ) 2023.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

PLASMA PROCESSES AND POLYMERS Vol. 20 ( 5 ) 2023.5

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (C5H6O2) were detected formed by interactions of lactate or its fragments with •OH, organic radicals, and H2O2. 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 Reviewed

Leukocyte Depletion and Size-Based Enrichment of Circulating Tumor Cells Using a Pressure-Sensing Microfiltration Device Reviewed 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 Vol. 3 ( 2 ) page： 113 - 119 2023.4

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 210 page： 111863 - 111863 2023.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Vacuum

The effects of substrate temperature (Ts) on the etch rate (ER) of the PECVD-prepared SiN, SiO2 and amorphous carbon (a-C) films, and their selectivity were investigated with a CF4/H2 plasma. The ERs for the SiN at all Ts were higher than that for the SiO2 films. As Ts was decreased from 50 to −20 °C, the ER for the SiN decreased. Contrarily, the ER of the SiO2 films increased. The etching selectivity of SiN over SiO2 reached to near unity when the Ts 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 Ts. The fluorocarbon (FC) thickness was greater for the SiO2 films than that of the SiN. The lower ER for the SiO2 was therefore attributed to the thicker FC layer and resultant etching mechanism. As the Ts was decreased, the FC thickness on the SiO2 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 Reviewed

High-performance glass filters for capturing and culturing circulating tumor cells and cancer-associated fibroblasts Reviewed 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 Vol. 13 ( 1 ) page： 4130 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed 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 Vol. 57 ( 3 ) page： 239 - 270 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 57 ( 3 ) page： 161 - 173 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

FREE RADICAL RESEARCH Vol. 57 ( 2 ) page： 91 - 104 2023.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

SAINS MALAYSIANA Vol. 52 ( 2 ) page： 599 - 611 2023.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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 Vol. 114 page： 749 - 749 2023.2

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

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 Vol. 114 page： 1340 - 1340 2023.2

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 Reviewed

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

JOURNAL OF APPLIED PHYSICS Vol. 133 ( 4 ) 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed 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 Vol. 862 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

GENES AND ENVIRONMENT Vol. 45 ( 1 ) page： 3 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 H2O2. H2O2 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 H2O2 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 Reviewed Open Access

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

FRONTIERS IN PHYSICS Vol. 10 2023.1

Plasma activated Ringer's lactate solution Reviewed

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

FREE RADICAL RESEARCH Vol. 57 ( 1 ) page： 14 - 20 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed 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 Vol. 62 ( SA ) 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 62 ( SA ) 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Selective isotropic atomic-layer etching of thin films by using dry chemical removal tool Reviewed

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

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

NANOMATERIALS Vol. 13 ( 1 ) 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 CH4 and H2 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 O2. 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-O2– 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

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

Proceedings of SPIE - The International Society for Optical Engineering Vol. 12499 2023

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Impact of microsecond-pulsed plasma-activated water on papaya seed germination and seedling growth Reviewed

Free radical formation induced by cold atmospheric plasma and its biological implications-Comparison with ionizing radiation- Reviewed

Kondo Taakshi, Tanaka Hiromasa, Ishikawa Kenji, Hori Masaru

Vol. 74 ( 2 ) page： 120 - 126 2023

総説：プラズマなどで処理された水の多様性 Reviewed

石川健治

静電気学会誌 Vol. 46 page： 209 2023

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

CHINESE PHYSICS B Vol. 31 ( 12 ) 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 NO2, NO3, and H2O2 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 Reviewed Open Access

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

COATINGS Vol. 12 ( 12 ) 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

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

SCIENTIFIC REPORTS Vol. 12 ( 1 ) page： 20394 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

ACS APPLIED MATERIALS & INTERFACES Vol. 14 ( 47 ) page： 53413 - 53420 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

VACUUM Vol. 205 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Vacuum

In the growth of hydrogenated amorphous carbon (a-C:H) films by plasma enhanced chemical vapor deposition (PECVD) with H2, CH4 and C3H6 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 (O2) 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 C3H3 and C5H5, contributed to a decrease in the etching rate, whereas hydrogen-rich radicals, such as CHx (x=1,2,3,4), C2H5, C4H9, and C5H9,11 induced an increase in the etching rate by the O2 plasma. (200 words)

DOI： 10.1016/j.vacuum.2022.111351

Dissociation channels of c-C4F8 to C2F4 in reactive plasma Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( 10 ) 2022.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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

In-liquid plasma synthesis of iron-nitrogen-doped carbon nanoflakes with high catalytic activity Reviewed

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

PLASMA PROCESSES AND POLYMERS Vol. 19 ( 8 ) 2022.8

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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 Vol. 61 ( SI ) 2022.7

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

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 24 ( 22 ) page： 13883 - 13896 2022.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Chemistry Chemical Physics

We consider the corona model and local thermal equilibrium approximations of a real plasma to measure the electron temperature (Te) and density (ne), respectively, using the optical emission spectroscopy (OES) method in dual-frequency pulsed capacitively coupled plasmas (CCPs) in a reactive mixture of Ar/O2/C4F8 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 Te values. In the second method, we simultaneously used the Boltzmann and Saha equations to determine the ne value using the line intensity ratio and the value of Te. Time-resolved measurements of Te and ne were performed for completeness, and the insight of the pulsed discharge was investigated. Time evolution of ne and Te 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 ne 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 Reviewed

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

PLASMA PROCESSES AND POLYMERS Vol. 19 ( 6 ) 2022.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Processes and Polymers

Reduction of SnO2 to form spherical Sn particles and Sn etching are obtained by floating wire (FW)-assisted medium-pressure H2/Ar plasma. High-density H2/Ar plasma (1014 cm−3) with a larger treatment area at medium pressure (10 kPa) produces a two-times higher removal rate of SnO2 (0.111 mg/min) than that at atmospheric pressure with the same treatment area of 300 mm2. SnO2 film is removed from the glass surface by a two-step process involving (1) reduction of SnO2 by FW-H2/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 Reviewed

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 Vol. 15 ( 5 ) 2022.5

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Vol. 40 ( 2 ) 2022.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

AIP ADVANCES Vol. 12 ( 2 ) 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed 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 Vol. 61 ( SA ) 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed International coauthorship 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 Vol. 61 ( SA ) page： SA0808 2022.1

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

Ishikawa, K

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( SA ) page： SA0802 2022.1

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed International coauthorship 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 Vol. 61 ( SA ) page： SA0805 2022.1

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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

Plasma Diagnostics and Characteristics of Hydrofluorocarbon Films in Capacitively Coupled CF<inf>4</inf>/H<inf>2</inf>Plasmas Reviewed

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

IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings Vol. 2022-December 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Wide range applications of process plasma diagnostics using vacuum ultraviolet absorption spectroscopy Reviewed

Takeda, K; Ishikawa, K; Hori, M

REVIEWS OF MODERN PLASMA PHYSICS Vol. 6 ( 1 ) 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

COATINGS Vol. 11 ( 12 ) page： 1535 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (CF4/D2 and CF4/H2 ) and substrate temperature (Ts, from −20 to 50◦ C) on etch rates (ERs) of the PECVD SiN films were investigated. The etch rate performed by CF4/D2 plasma was higher than one obtained by CF4/H2 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 CF4/D2 plasma in comparison with CF4/H2 . 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 CF4/H2 plasma. The plasma density, gas phase concentration and FC thickness were not responsible for the higher etch rate in the CF4/D2 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 CF4/D2 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 CF4/H2 at −20◦ C, the increase in ER was attributed to a thinner FC layer and surface reactions. On the contrary, in the CF4/D2 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 Reviewed

プラズマがん治療 Invited Reviewed

石川健治，堀勝

静電気学会誌 Vol. 45 ( 6 ) page： 206 - 212 2021.11

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

PLASMA PROCESSES AND POLYMERS Vol. 18 ( 11 ) page： 2100078 2021.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Processes and Polymers

The dependences of etching characteristics on substrate temperature (Ts, 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 CF4/H2 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 Ts, due to the different FC thickness and etching mechanisms proposed. The formation of the N−Hx layer on PE-SiN at low temperature caused the decrease in ER. For the LP-SiN, the weak dependences of Ts 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 Reviewed

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 Vol. 18 ( 10 ) page： 2100056 2021.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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-H2O2 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 Reviewed 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 Vol. 11 ( 1 ) page： 18488 2021.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Leading edge of transcendental dry etching technology realizing advanced decice structures Invited Reviewed

Kenji Ishikawa, and Keigo Takeda

Journal of plasma and fusion research Vol. 97 ( 9 ) page： 534 - 536 2021.9

Effects of free radicals generated by atmospheric pressure plasma on physical actions and biochemical relaxations (PACR) Invited Reviewed

Kenji Ishikawa, Hiroshi Hashizume, Camelia Miron, Hiromasa Tanaka, and Masaru Hori

Radiation biology research communications Vol. 56 ( 3 ) page： 280 - 294 2021.9

Reaction control of atomic layer and low dame processes for plasma etching of nitride semiconductor Invited Reviewed

Takayoshi Tsutsumi, Kenji Ishikawa, Hiroki Kondo, Makoto Sekine, and Masaru Hori

Journal of plasma and fusion research Vol. 97 ( 9 ) page： 517 - 521 2021.9

Leading edge of transcendental dry etching technology realizing advanced decice structures Invited Reviewed

Kenji Ishikawa, and Keigo Takeda

Journal of plasma and fusion research Vol. 97 ( 9 ) page： 508 - 510 2021.9

Novel Method of Rebound Tailing Pulse (RTP) for Water Dissociation Reviewed

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

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 49 ( 9 ) page： 2893 - 2900 2021.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Lysosomal nitric oxide determines transition from autophagy to ferroptosis after exposure to plasma-activated Ringer's lactate Reviewed 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 Vol. 43 page： 101989 2021.7

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

APPLIED PHYSICS EXPRESS Vol. 14 ( 6 ) page： 067002 2021.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

PLASMA SOURCES SCIENCE & TECHNOLOGY Vol. 30 ( 4 ) 2021.4

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

APPLIED SURFACE SCIENCE Vol. 542 page： 148550 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 CF4/H2 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 Reviewed

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

APPLIED SURFACE SCIENCE Vol. 541 page： 148439 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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 CH2F and CHF2 related ions and radicals from a 1,1,2-trifluoroethane (CH2FCHF2) parent gas. The etch selectivity among silicon nitride (SiN), silicon dioxide (SiO2) and poly-Si films using CH2FCHF2 plasma mixed with O2 and Ar was investigated. The effects of the CH2FCHF2 and O2 partial pressures on the composition of CHF2+ and CH2F+ ions, which were measured with a quadrupole mass spectrometer, and on the possible reactions with respect to the CH2FCHF2 and O2 mixed gas phase were investigated using quantum chemical calculations. The etch selectivity was investigated through surface etching reactions for SiN, SiO2, and poly-Si films.

DOI： 10.1016/j.apsusc.2020.148439

FOREWORD Mechanistic understanding of cold atmospheric plasma applications Reviewed Open Access

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( 2 ) 2021.2

Growth inhibition effect on Trypanosoma brucei gambiense by the oxidative stress supplied from low-temperature plasma at atmospheric pressure Reviewed 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 Vol. 60 ( 2 ) page： 020601 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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) Reviewed Open Access

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

NANOMATERIALS Vol. 11 ( 2 ) page： 1 - 11 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed International coauthorship Open Access

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

SCIENTIFIC REPORTS Vol. 11 ( 1 ) page： 2539 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Vol. 60 ( 1 ) page： 010502 2021.1

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

Japanese Journal of Applied Physics Vol. 60 ( 1 ) page： 010906 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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 Vol. 18 ( 1 ) page： 2000181 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

CURRENT MEDICINAL CHEMISTRY Vol. 28 ( 41 ) page： 8549 - 8558 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Numerical analysis of high-electron-density atmospheric pressure argon streamer under a pin-to-plane electrode geometry: Effects of applying voltage polarity Reviewed

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

47th EPS Conference on Plasma Physics, EPS 2021 Vol. 2021-June page： 45 - 48 2021

Reaction science of layer-by-layer thinning of graphene with oxygen neutrals at room temperature Reviewed

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

CARBON Vol. 170 page： 93 - 99 2020.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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) Reviewed

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

JOURNAL OF CRYSTAL GROWTH Vol. 549 page： 125863 2020.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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 N2*/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 Reviewed

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

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 53 ( 43 ) page： 534302 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

SCIENTIFIC REPORTS Vol. 10 ( 1 ) page： 17770 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Scientific Reports

A green method to synthesize spherical Sn particles by reducing SnO2 film in atmospheric-pressure H2/Ar plasma at low temperatures for various applications is presented. The floating wire-assisted remotely-generated plasma with a mixture of 0.05% H2/Ar gas formed spherical metallic Sn particles by reducing a SnO2 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 SnO2/glass substrate was placed for plasma treatment. The process has been modeled on the spherical Sn formation based on the reduction of SnO2 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 Reviewed 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 Vol. 5 ( 41 ) page： 26776 - 26785 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

Applied Physics Express Vol. 13 ( 10 ) 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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 Vol. 17 ( 10 ) page： 1900259 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed 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 Vol. 6 ( 1 ) page： 83 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (O2• −) 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

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

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

APPLIED PHYSICS EXPRESS Vol. 13 ( 8 ) page： 086001 2020.8

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

PROCESSES Vol. 8 ( 8 ) page： 1002 2020.8

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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 Vol. 688 page： 108414 2020.7

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Vol. 38 ( 4 ) page： 042602 2020.7

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed Open Access

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

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 53 ( 26 ) page： 265204 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

APPLIED PHYSICS EXPRESS Vol. 13 ( 6 ) page： 066001 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

PLASMA SCIENCE & TECHNOLOGY Vol. 22 ( 6 ) page： 065404 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Electronic properties and primary dissociation channels of fluoromethane compounds Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SJ ) page： SJJE02 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

We investigated fluoromethane compounds (CF4, CF3, CHF3, CH2F2, and CH3F) 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 CHF3 and CH3F 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

Electron spin resonance as a tool to monitor the influence of novel processing technologies on food properties Reviewed International coauthorship

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

TRENDS IN FOOD SCIENCE & TECHNOLOGY Vol. 100 page： 77 - 87 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

Dry Process FOREWORD Reviewed

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 Vol. 59 ( SJ ) 2020.6

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

CARBON Vol. 161 page： 403 - 412 2020.5

Language：English Publishing type：Research paper (scientific journal) Publisher：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 CH4/H2 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 Reviewed

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 Vol. 104 2020.4

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (ΓEi), 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 H2 and CH4 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 ΓEi. 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 Reviewed

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

CHEMNANOMAT Vol. 6 ( 4 ) page： 604 - 609 2020.4

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (FWHMG) 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

Interaction of oxygen with polystyrene and polyethylene polymer films: A mechanistic study Reviewed International coauthorship

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 Vol. 127 ( 2 ) 2020.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

Japanese Journal of Applied Physics Vol. 60 ( 1 ) page： 010503 2020

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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 page： 882 - 883 2020

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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.

Cell deposition and isolation with micropipette control over liquid interface motion in microfluidic channel Reviewed

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 page： 679 - 680 2020

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 Reviewed

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

2020 INTERNATIONAL SYMPOSIUM ON SEMICONDUCTOR MANUFACTURING (ISSM) Vol. 2020-December 2020

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 52 ( 47 ) 2019.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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 CHF3/O2 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 CHF3/O2 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 (NH4)xTiFy, 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 CHF3/O2 downstream plasma, which was also used for isotropic ALE of Si3N4.

DOI： 10.1088/1361-6463/ab3cf3

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

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 Vol. 37 ( 6 ) 2019.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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 N2 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

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

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

Tanaka Hiromasa, Mizuno Masaaki, Katsumata Yuko, Ishikawa Kenji, Kondo Hiroki, Hashizume Hiroshi, Okazaki Yasumasa, Toyokuni Shinya, Nakamura Kae, Yoshikawa Nobuhisa, Kajiyama Hiroaki, Kikkawa Fumitaka, Hori Masaru

SCIENTIFIC REPORTS Vol. 9 ( 1 ) page： 13657 2019.9

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

C-JOURNAL OF CARBON RESEARCH Vol. 5 ( 3 ) 2019.9

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

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

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Vol. 37 ( 5 ) 2019.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

Self-limiting reactions of ammonium salt in CHF3/O2 downstream plasma were demonstrated for thermal-cyclic atomic layer etching (ALE) of Si3N4. In situ x-ray photoelectron spectroscopy analysis shows that an (NH4)2SiF6 by-product of the same thickness forms on Si3N4 in a wide gas composition range. The (NH4)2SiF6 layer prevents etching of Si3N4 during continuous plasma exposure in that wide range. The (NH4)2SiF6 layer was sublimated by heating, which was consistent with the result of the thermodynamic calculation. The reactions of the (NH4)2SiF6 layer in CHF3/O2 downstream plasma are used for thermal-cyclic ALE of Si3N4 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

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

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

PLASMA PROCESSES AND POLYMERS Vol. 16 ( 9 ) 2019.9

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

PLASMA PROCESSES AND POLYMERS Vol. 16 ( 8 ) 2019.8

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

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

ACS Applied Bio Materials Vol. 2 ( 7 ) page： 2698 - 2702 2019.7

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Plasma-activated solution alters the morphological dynamics of supported lipid bilayers observed by high-speed atomic force microscopy Reviewed

Rethinking surface reactions in nanoscale dry processes toward atomic precision and beyond: a physics and chemistry perspective Reviewed International coauthorship Open Access

Ishikawa Kenji, Ishijima Tatsuo, Shirafuji Tatsuru, Armini Silvia, Despiau-Pujo Emilie, Gottscho Richard A., Kanarik Keren J., Leusink Gert J., Marchack Nathan, Murayama Takahide, Morikawa Yasuhiro, Oehrlein Gottlieb S., Park Sangwuk, Hayashi Hisataka, Kinoshita Keizo

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SE ) 2019.6

Yamaoka Sotaro, Kondo Hiroki, Hashizume Hiroshi, Ishikawa Kenji, Tanaka Hiromasa, Hori Masaru

APPLIED PHYSICS EXPRESS Vol. 12 ( 6 ) 2019.6

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

Iwase Taku, Kamaji Yoshito, Kang Song Yun, Koga Kazunori, Kuboi Nobuyuki, Nakamura Moritaka, Negishi Nobuyuki, Nozaki Tomohiro, Nunomura Shota, Ogawa Daisuke, Omura Mitsuhiro, Shimizu Tetsuji, Shinoda Kazunori, Sonoda Yasushi, Suzuki Haruka, Takahashi Kazuo, Tsutsumi Takayoshi, Yoshikawa Kenichi, Ishijima Tatsuo, Ishikawa Kenji

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SE ) 2019.6

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SE ) 2019.6

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SE ) 2019.6

Electronic properties and primarily dissociation channels of fluoroethane compounds Reviewed

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

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SE ) 2019.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Electronic properties of fluoroethane compounds except C2H5F, C2H4F2, CH3CF3, C2H2F4, and C2F6 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-C2H2F4. 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 Reviewed International coauthorship

Zhang Yan, Ishikawa Kenji, Mozetic Miran, Tsutsumi Takayoshi, Kondo Hiroki, Sekine Makoto, Hori Masaru

PLASMA PROCESSES AND POLYMERS Vol. 16 ( 6 ) 2019.6

Laser-drilling formation of through-glass-via (TGV) on polymer-laminated glass Reviewed

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

JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS Vol. 30 ( 11 ) page： 10183 - 10190 2019.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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 Vol. 37 ( 3 ) 2019.5

Language：English Publishing type：Research paper (scientific journal) Publisher：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 N2 and H2 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)) Reviewed Open Access

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

Micro and Nano Engineering Vol. 3 page： 92 - 92 2019.5

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

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

Micro and Nano Engineering Vol. 3 page： 1 - 6 2019.5

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：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(–]CH3)2) 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–]CH3) 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

Facile synthesis of SnO₂-graphene composites employing nonthermal plasma and SnO₂ nanoparticles-dispersed ethanol Reviewed

Borude Ranjit R., Sugiura Hirotsugu, Ishikawa Kenji, Tsutsumi Takayoshi, Kondo Hiroki, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 52 ( 17 ) 2019.4

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

Takeda Keigo, Yamada Hiromasa, Ishikawa Kenji, Sakakita Hajime, Kim Jaeho, Ueda Masashi, Ikeda Jun-ichiro, Akimoto Yoshihiro, Kataoka Yosky, Yokoyama Naoaki, Ikehara Yuzuru, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 52 ( 16 ) 2019.4

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 Reviewed Open Access

Niitsu Kiichi, Nakanishi Taiki, Murakami Shunya, Matsunaga Maya, Kobayashi Atsuki, Karim Nissar Mohammad, Ito Jun, Ozawa Naoya, Hase Tetsunari, Tanaka Hiromasa, Sato Mitsuo, Kondo Hiroki, Ishikawa Kenji, Odaka Hidefumi, Hasegawa Yoshinori, Hori Masaru, Nakazato Kazuo

IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS Vol. 13 ( 2 ) page： 470 - 479 2019.4

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

Imai Shun, Naito Kenichi, Kondo Hiroki, Cho Hyung Jun, Ishikawa Kenji, Tsutsumi Takayoshi, Sekine Makoto, Hiramatsu Mineo, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 52 ( 10 ) 2019.3

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

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 Vol. 58 ( 3 ) 2019.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Amorphous carbon (a-C) thin films were deposited under the control of C2 radical density using radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD) with CH4/H2 plasma. By actinometric monitoring of C2 emission intensities, the plasma parameters were precisely controlled by changing in CH4-containing plasma excitation power independent of H2 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 Reviewed

Tanide Atsushi, Nakamura Shohei, Horikoshi Akira, Takatsuji Shigeru, Kohno Motohiro, Kinose Kazuo, Nadahara Soichi, Ishikawa Kenji, Sekine Makoto, Hori Masaru

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Vol. 37 ( 2 ) 2019.3

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 Reviewed

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

C-JOURNAL OF CARBON RESEARCH Vol. 5 ( 1 ) 2019.3

Electrochemical Reaction in Hydrogen Peroxide and Structural Change of Platinum Nanoparticle-Supported Carbon Nanowalls Grown Using Plasma-Enhanced Chemical Vapor Deposition Reviewed

Tomatsu, M; Hiramatsu, M; Kondo, H; Ishikawa, K; Tsutsumi, T; Sekine, M; Hori, M

C-JOURNAL OF CARBON RESEARCH Vol. 5 ( 1 ) 2019.3

Non-thermal plasma-activated medium modified metabolomic profiles in the glycolysis of U251SP glioblastoma Reviewed

Kurake Naoyuki, Ishikawa Kenji, Tanaka Hiromasa, Hashizume Hiroshi, Nakamura Kae, Kajiyama Hiroaki, Toyokuni Shinya, Kikkawa Fumitaka, Mizuno Masaaki, Hori Masaru

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS Vol. 662 page： 83 - 92 2019.2

Remotely floating wire-assisted generation of high-density atmospheric pressure plasma and SF6-added plasma etching of quartz glass Reviewed

Thi-Thuy-Nga Nguyen, Sasaki Minoru, Odaka Hidefumi, Tsutsumi Takayoshi, Ishikawa Kenji, Hori Masaru

JOURNAL OF APPLIED PHYSICS Vol. 125 ( 6 ) 2019.2

Liquid dynamics in response to an impinging low-temperature plasma jet Reviewed International coauthorship

Brubaker T. R., Ishikawa K., Kondo H., Tsutsumi T., Hashizume H., Tanaka H., Knecht S. D., Bilen S. G., Hori M.

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 52 ( 7 ) 2019.2

Effect of electrical stimulation on proliferation and bone-formation by osteoblast-like cells cultured on carbon nanowalls scaffolds Reviewed

Ichikawa Tomonori, Tanaka Suiki, Kondo Hiroki, Ishikawa Kenji, Tsutsumi Takayoshi, Sekine Makoto, Hori Masaru

APPLIED PHYSICS EXPRESS Vol. 12 ( 2 ) 2019.2

Adhesion enhancement and amine reduction using film redeposited at the interface of a stack of plasma-enhanced CVD dielectrics for Cu/low-k interconnects Reviewed

Miyajima Hideshi, Watanabe Kei, Ishikawa Kenji, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( 2 ) 2019.2

Narrow free-standing features fabricated by top-down self-limited trimming of organic materials using precisely temperature-controlled plasma etching system Reviewed

Fukunaga Yusuke, Tsutsumi Takayoshi, Kondo Hiroki, Ishikawa Kenji, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( 2 ) 2019.2

Hetero-epitaxial growth of a GaN film by the combination of magnetron sputtering with Ar/Cl-2 gas mixtures and a separate supply of nitrogen precursors from a high density radical source Reviewed

Tanide Atsushi, Nakamura Shohei, Horikoshi Akira, Takatsuji Shigeru, Kohno Motohiro, Kinose Kazuo, Nadahara Soichi, Nishikawa Masazumi, Ebe Akinori, Ishikawa Kenji, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SA ) 2019.2

Modifications of surface and bulk properties of magnetron-sputtered carbon films employing a post-treatment of atmospheric pressure plasma Reviewed

Borude Ranjit R., Sugiura Hirotsugu, Ishikawa Kenji, Tsutsumi Takayoshi, Kondo Hiroki, Han Jeon Geon, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( SA ) 2019.2

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 Reviewed

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

ACS APPLIED NANO MATERIALS Vol. 2 ( 2 ) page： 649 - 654 2019.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Applied Nano Materials

The in situ binding of tin oxide (SnO2) 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 (SnCl2·2H2O) 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/H-2 plasma-enhanced chemical vapor deposition Reviewed

Imai Shun, Kondo Hiroki, Hyungjun Cho, Ishikawa Kenji, Tsutsumi Takayoshi, Sekine Makoto, Hiramatsu Mineo, Hori Masaru

APPLIED PHYSICS EXPRESS Vol. 12 ( 1 ) 2019.1

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 Vol. 139 ( 1 ) page： 27 - 28 2019.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

Tanaka Hiromasa, Mizuno Masaaki, Ishikawa Kenji, Toyokuni Shinya, Kajiyama Hiroaki, Kikkawa Fumitaka, Hori Masaru

BIOLOGICAL CHEMISTRY Vol. 400 ( 1 ) page： 87 - 91 2019.1

Single-cell microscopic raman spectroscopy for rapid microbial detection Reviewed

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 page： 1374 - 1375 2019

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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.

Reaction mechanisms between chlorine plasma and a spin-on-type polymer mask for high-temperature plasma etching Reviewed

Effect of N-2/H-2 plasma on GaN substrate cleaning for homoepitaxial GaN growth by radical-enhanced metalorganic chemical vapor deposition (REMOCVD) Reviewed Open Access

Amalraj Frank Wilson, Dhasiyan Arun Kumar, Lu Yi, Shimizu Naohiro, Oda Osamu, Ishikawa Kenji, Kondo Hiroki, Sekine Makoto, Ikarashi Nobuyuki, Hori Masaru

AIP ADVANCES Vol. 8 ( 11 ) 2018.11

Zhang Yan, Imamura Masato, Ishikawa Kenji, Tsutsumi Takayoshi, Kondo Hiroki, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 10 ) 2018.10

Elevated-temperature etching of gallium nitride (GaN) in dual-frequency capacitively coupled plasma of CH4/H-2 at 300-500 degrees C Reviewed

Kako Takashi, Liu Zecheng, Ishikawa Kenji, Kondo Hiroki, Oda Osamu, Sekine Makoto, Hori Masaru

VACUUM Vol. 156 page： 219 - 223 2018.10

Cytotoxic effects of plasma-irradiated fullerenol Reviewed

Kanno Daiki, Tanaka Hiromasa, Ishikawa Kenji, Hashizume Hiroshi, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 51 ( 37 ) 2018.9

大気圧プラズマ処理による異種材料接合 Invited Reviewed

近藤博基, 堤隆嘉, 石川健治, 関根誠, 堀勝

化学工学 Vol. 82 ( 9 ) 2018.9

New hopes for plasma-based cancer treatment Reviewed

Hiromasa Tanaka, Masaaki Mizuno, Kenji Ishikawa, Shinya Toyokuni, Hiroaki Kajiyama, Fumitaka Kikkawa, and Masaru Hori

Plasma Vol. 1 ( 1 ) page： 150 - 155 2018.9

Real-time control of a wafer temperature for uniform plasma process Reviewed

Tsutsumi T., Fuknaga Y., Ishikawa K., Kondo H., Sekine M., Hori M.

IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings Vol. 2018-December 2018.7

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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

Dissociative properties of 1,1,1,2-tetrafluoroethane obtained by computational chemistry Reviewed

Hayashi Toshio, Ishikawa Kenji, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Temperature dependence on plasma-induced damage and chemical reactions in GaN etching processes using chlorine plasma Reviewed

Liu Zecheng, Ishikawa Kenji, Imamura Masato, Tsutsumi Takayoshi, Kondo Hiroki, Oda Osamu, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Progress in nanoscale dry processes for fabrication of high-aspect-ratio features: How can we control critical dimension uniformity at the bottom? Reviewed International coauthorship Open Access

Ishikawa Kenji, Karahashi Kazuhiro, Ishijima Tatsuo, Cho Sung Il, Elliott Simon, Hausmann Dennis, Mocuta Dan, Wilson Aaron, Kinoshita Keizo

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Low-autofluorescence fluoropolymer membrane filters for cell filtration Reviewed Open Access

Kihara Naoto, Kuboyama Daiki, Onoshima Daisuke, Ishikawa Kenji, Tanaka Hiromasa, Ozawa Naoya, Hase Tetsunari, Koguchi Ryohei, Yukawa Hiroshi, Odaka Hidefumi, Hasegawa Yoshinori, Baba Yoshinobu, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Impact of helium pressure in arc plasma synthesis on crystallinity of single-walled carbon nanotubes Reviewed

Ando Atsushi, Takeda Keigo, Ohta Takayuki, Ito Masafumi, Hiramatsu Mineo, Ishikawa Kenji, Kondo Hiroki, Sekine Makoto, Suzuki Tomoko, Inoue Sakae, Ando Yoshinori, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Effects of gas residence time of CH4/H-2 on sp(2) fraction of amorphous carbon films and dissociated methyl density during radical-injection plasma-enhanced chemical vapor deposition Reviewed

Sugiura Hirotsugu, Jia Lingyun, Kondo Hiroki, Ishikawa Kenji, Tsutsumi Takayoshi, Hayashi Toshio, Takeda Keigo, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Dry Process FOREWORD Reviewed

Karahashi Kazuhiro, Kinoshita Keizo, Higashi Seiichiro, Ishikawa Kenji, Ishijima Tatsuo, Kuboi Nobuyuki

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 6 ) 2018.6

Nanographene synthesized in triple-phase plasmas as a highly durable support of catalysts for polymer electrolyte fuel cells Reviewed

Amano Tomoki, Kondo Hiroki, Takeda Keigo, Ishikawa Kenji, Hiramatsu Mineo, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 4 ) 2018.4

Oxygen reduction reaction properties of nitrogen-incorporated nanographenes synthesized using in-liquid plasma from mixture of ethanol and iron phthalocyanine Reviewed

Amano Tomoki, Kondo Hiroki, Takeda Keigo, Ishikawa Kenji, Hiramatsu Mineo, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 4 ) 2018.4

Cytotoxicity of cancer HeLa cells sensitivity to normal MCF10A cells in cultivations with cell culture medium treated by microwave-excited atmospheric pressure plasmas Reviewed

Takahashi Yohei, Taki Yusuke, Takeda Keigo, Hashizume Hiroshi, Tanaka Hiromasa, Ishikawa Kenji, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 51 ( 11 ) 2018.3

Free radical generation by non-equilibrium atmospheric pressure plasma in alcohol-water mixtures: an EPR-spin trapping study Reviewed

Uchiyama Hidefumi, Ishikawa Kenji, Zhao Qing-Li, Andocs Gabor, Nojima Nobuyuki, Takeda Keigo, Krishna Murali C., Ishijima Tatsuo, Matsuya Yuji, Hori Masaru, Noguchi Kyo, Kondo Takashi

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 51 ( 9 ) 2018.3

Facile fabrication of a poly(ethylene terephthalate) membrane filter with precise arrangement of through-holes Reviewed

Kihara Naoto, Odaka Hidefumi, Kuboyama Daiki, Onoshima Daisuke, Ishikawa Kenji, Baba Yoshinobu, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 3 ) 2018.3

Reduced HeLa cell viability in methionine-containing cell culture medium irradiated with microwave-excited atmospheric-pressure plasma Reviewed

Takahashi Yohei, Taki Yusuke, Takeda Keigo, Hashizume Hiroshi, Tanaka Hiromasa, Ishikawa Kenji, Hori Masaru

PLASMA PROCESSES AND POLYMERS Vol. 15 ( 3 ) 2018.3

Nanographene synthesis employing in-liquid plasmas with alcohols or hydrocarbons Reviewed

Ando Atsushi, Ishikawa Kenji, Kondo Hiroki, Tsutsumi Takayoshi, Takeda Keigo, Ohta Takayuki, Ito Masafumi, Hiramatsu Mineo, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 2 ) 2018.2

Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials FOREWORD Reviewed

Naritsuka Shigeya, Miyazaki Seiichi, Fujiwara Yasufumi, Hiramatsu Mineo, Inoue Yasushi, Ishikawa Kenji, Ito Masafumi, Itoh Takashi, Kasu Makoto, Miyake Hideto, Sasaki Minoru, Shirafuji Tatsuru, Suda Yoshiyuki

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 1 ) 2018.1

Selective production of reactive oxygen and nitrogen species in the plasma-treated water by using a nonthermal high-frequency plasma jet Reviewed

Uchida Giichiro, Takenaka Kosuke, Takeda Keigo, Ishikawa Kenji, Hori Masaru, Setsuhara Yuichi

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 57 ( 1 ) 2018.1

Rapid growth of micron-sized graphene flakes using in-liquid plasma employing iron phthalocyanine-added ethanol Reviewed

Amano Tomoki, Kondo Hiroki, Ishikawa Kenji, Tsutsumi Takayoshi, Takeda Keigo, Hiramatsu Mineo, Sekine Makoto, Hori Masaru

APPLIED PHYSICS EXPRESS Vol. 11 ( 1 ) 2018.1

Plasma-activated medium (PAM) kills human cancer-initiating cells Reviewed Open Access

Ikeda Jun-ichiro, Tanaka Hiromasa, Ishikawa Kenji, Sakakita Hajime, Ikehara Yuzuru, Hori Masaru

PATHOLOGY INTERNATIONAL Vol. 68 ( 1 ) page： 23 - 30 2018.1

Electron impact ionization of perfluoro-methyl-vinyl-ether C3F6O Reviewed

Kondo Yusuke, Ishikawa Kenji, Hayashi Toshio, Sekine Makoto, Hori Masaru

PLASMA SOURCES SCIENCE & TECHNOLOGY Vol. 27 ( 1 ) 2018.1

Cell Deposition Microchip with Micropipette Control over Liquid Interface Motion Reviewed

Onoshima Daisuke, Hattori Yuya, Yukawa Hiroshi, Ishikawa Kenji, Hori Masaru, Baba Yoshinobu

CELL MEDICINE Vol. 10 page： 2155179017733152 2018

Isotropic atomic level etching of tungsten using formation and desorption of tungsten fluoride Reviewed

Shinoda Kazunori, Miyoshi Nobuya, Kobayashi Hiroyuki, Hanaoka Yuko, Kawamura Kohei, Izawa Masaru, Ishikawa Kenji, Hori Masaru

ADVANCED ETCH TECHNOLOGY FOR NANOPATTERNING VII Vol. 10589 2018

Glioblastoma Cell Lines Display Different Sensitivities to Plasma-Activated Medium Reviewed

Tanaka Hiromasa, Mizuno Masaaki, Ishikawa Kenji, Takeda Keigo, Hashizume Hiroshi, Nakamura Kae, Utsumi Fumi, Kajiyama Hiroaki, Okazaki Yasumasa, Toyokuni Shinya, Akiyama Shinichi, Maruyama Shoichi, Kikkawa Fumitaka, Hori Masaru

IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES Vol. 2 ( 2 ) page： 99 - 102 2018

Oncogene mutation analysis of circulating tumor cells using single-cell membrane separation and DNA amplification Reviewed

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 Vol. 3 page： 1291 - 1293 2018

Language：English Publishing type：Research paper (international conference proceedings) Publisher：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 Reviewed

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 Vol. 3 page： 1409 - 1410 2018

Language：English Publishing type：Research paper (scientific journal) Publisher：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.

Dependence of absolute photon flux on infrared absorbance alteration and surface roughness on photoresist polymers irradiated with vacuum ultraviolet photons emitted from HBr plasma Reviewed

Dynamic analysis of reactive oxygen nitrogen species in plasma-activated culture medium by UV absorption spectroscopy Reviewed International coauthorship

Brubaker Timothy R., Ishikawa Kenji, Takeda Keigo, Oh Jun-Seok, Kondo Hiroki, Hashizume Hiroshi, Tanaka Hiromasa, Knecht Sean D., Bilen Sven G., Hori Masaru

JOURNAL OF APPLIED PHYSICS Vol. 122 ( 21 ) 2017.12

Zhang Yan, Takeuchi Takuya, Ishikawa Kenji, Hayashi Toshio, Takeda Keigo, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 12 ) 2017.12

State of the art in medical applications using non-thermal atmospheric pressure plasma Reviewed International coauthorship

Tanaka H., Ishikawa K., Mizuno M., Toyokuni S., Kajiyama H., Kikkawa F., Metelmann H.R., Hori M.

Reviews of Modern Plasma Physics Vol. 1 ( 1 ) 2017.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed

Furuta Ryo, Kurake Naoyuki, Ishikawa Kenji, Takeda Keigo, Hashizume Hiroshi, Tanaka Hiromasa, Kondo Hiroki, Sekine Makoto, Hori Masaru

PLASMA PROCESSES AND POLYMERS Vol. 14 ( 11 ) 2017.11

Surface roughening of photoresist after change of the photon/radical and ion treatment sequence Reviewed

Zhang Yan, Takeuchi Takuya, Ishikawa Kenji, Takeda Keigo, Kondo Hiroki, Sekine Makoto, Hori Masaru

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Vol. 35 ( 6 ) 2017.11

最先端プラズマバイオ技術 Invited Reviewed

堀勝，石川健治，近藤隆，田中宏昌，橋爪博司

放射線化学 page： 3 - 14 2017.10

Crystallization of calcium oxalate dihydrate in a buffered calcium-containing glucose solution by irradiation with non-equilibrium atmospheric pressure plasma Reviewed

Kurake Naoyuki, Tanaka Hiromasa, Ishikawa Kenji, Nakamura Kae, Kajiyama Hiroaki, Kikkawa Fumitaka, Mizuno Masaaki, Ikehara Yuzuru, Hori Masaru

JOURNAL OF APPLIED PHYSICS Vol. 122 ( 14 ) 2017.10

High-durability catalytic electrode composed of Pt nanoparticle-supported carbon nanowalls synthesized by radical-injection plasma-enhanced chemical vapor deposition Reviewed

Imai Shun, Kondo Hiroki, Cho Hyungjun, Kano Hiroyuki, Ishikawa Kenji, Sekine Makoto, Hiramatsu Mineo, Ito Masafumi, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 50 ( 40 ) 2017.10

Cold atmospheric helium plasma causes synergistic enhancement in cell death with hyperthermia and an additive enhancement with radiation Reviewed Open Access

Moniruzzaman Rohan, Rehman Mati Ur, Zhao Qing-Li, Jawaid Paras, Takeda Keigo, Ishikawa Kenji, Hori Masaru, Tomihara Kei, Noguchi Kyo, Kondo Takashi, Noguchi Makoto

SCIENTIFIC REPORTS Vol. 7 ( 1 ) page： 11659 2017.9

Lipid droplets exhaustion with caspases activation in HeLa cells cultured in plasma-activated medium observed by multiplex coherent anti-Stokes Raman scattering microscopy Reviewed

Furuta Ryo, Kurake Naoyuki, Takeda Keigo, Ishikawa Kenji, Ohta Takayuki, Ito Masafumi, Hashizume Hiroshi, Tanaka Hiromasa, Kondo Hiroki, Sekine Makoto, Hori Masaru

BIOINTERPHASES Vol. 12 ( 3 ) page： 031006 2017.9

Thermally enhanced formation of photon-induced damage on GaN films in Cl<inf>2</inf> plasma Reviewed

Liu Z., Asano A., Imamura M., Ishikawa K., Takeda K., Kondo H., Oda O., Sekine M., Hori M.

Japanese Journal of Applied Physics Vol. 56 ( 9 ) 2017.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Deep ultraviolet (UV) photons emitted from Cl2 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 Cl2 plasma etching at high temperatures. The damages were formed thermally by photon-irradiations of plasma UV emissions with wavelengths of >258-306 nm from Cl2 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

Reduction of chlorine radical chemical etching of GaN under simultaneous plasma-emitted photon irradiation Reviewed

Liu Zecheng, Imamura Masato, Asano Atsuki, Ishikawa Kenji, Takeda Keigo, Kondo Hiroki, Oda Osamu, Sekine Makoto, Hori Masaru

APPLIED PHYSICS EXPRESS Vol. 10 ( 8 ) 2017.8

Temperature dependence of protection layer formation on organic trench sidewall in H-2/N-2 plasma etching with control of substrate temperature Reviewed

Fukunaga Yusuke, Tsutsumi Takayoshi, Takeda Keigo, Kondo Hiroki, Ishikawa Kenji, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 7 ) 2017.7

Intracellular-molecular changes in plasma-irradiated budding yeast cells studied using multiplex coherent anti-Stokes Raman scattering microscopy Reviewed

Furuta Ryo, Kurake Naoyuki, Ishikawa Kenji, Takeda Keigo, Hashizume Hiroshi, Kondo Hiroki, Ohta Takayuki, Ito Masafumi, Sekine Makoto, Hori Masaru

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 19 ( 21 ) page： 13438 - 13442 2017.6

Dry Process FOREWORD Reviewed

Ishikawa Kenji, Kinoshita Keizo, Higashi Seiichiro, Ichiki Takanori, Karahashi Kazuhiro, Kuboi Nobuyuki

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 6 ) 2017.6

Progress and prospects in nanoscale dry processes: How can we control atomic layer reactions? Reviewed International coauthorship Open Access

Ishikawa Kenji, Karahashi Kazuhiro, Ichiki Takanori, Chang Jane P., George Steven M., Kessels W. M. M., Lee Hae June, Tinck Stefan, Um Jung Hwan, Kinoshita Keizo

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 6 ) 2017.6

Hydrogen peroxide sensor based on carbon nanowalls grown by plasma-enhanced chemical vapor deposition Reviewed

Tomatsu Masakazu, Hiramatsu Mineo, Foord John S., Kondo Hiroki, Ishikawa Kenji, Sekine Makoto, Takeda Keigo, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 6 ) 2017.6

Growth of InN films by radical-enhanced metal organic chemical vapor deposition at a low temperature of 200 degrees C Reviewed

Takai Shinnosuke, Lu Yi, Oda Osamu, Takeda Keigo, Kondo Hiroki, Ishikawa Kenji, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 6 ) 2017.6

Electron behaviors in afterglow of synchronized dc-imposed pulsed fluorocarbon-based plasmas Reviewed

Ueyama Toshinari, Fukunaga Yusuke, Tsutsumi Takayoshi, Takeda Keigo, Kondo Hiroki, Ishikawa Kenji, Sekine Makoto, Iwata Manabu, Ohya Yoshinobu, Sugai Hideo, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 6 ) 2017.6

Selective atomic-level etching using two heating procedures, infrared irradiation and ion bombardment, for next-generation semiconductor device manufacturing Reviewed

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 Vol. 50 ( 19 ) 2017.5

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 Reviewed

Takeda Keigo, Ishikawa Kenji, Tanaka Hiromasa, Sekine Makoto, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 50 ( 19 ) 2017.5

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 Invited Reviewed

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 2017.5

Bactericidal pathway of Escherichia coli in buffered saline treated with oxygen radicals Reviewed

Kobayashi Tsuyoshi, Iwata Natsumi, Oh Jun-Seok, Hahizume Hiroshi, Ohta Takayuki, Takeda Keigo, Ishikawa Kenji, Hori Masaru, Ito Masafumi

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 50 ( 15 ) 2017.4

Effects of center dot OH and center dot NO radicals in the aqueous phase on H2O2 and NO2- generated in plasma-activated medium Reviewed

Kurake Naoyuki, Tanaka Hiromasa, Ishikawa Kenji, Takeda Keigo, Hashizume Hiroshi, Nakamura Kae, Kajiyama Hiroaki, Kondo Takashi, Kikkawa Fumitaka, Mizuno Masaaki, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 50 ( 15 ) 2017.3

Spatial profiles of interelectrode electron density in direct current superposed dual-frequency capacitively coupled plasmas Reviewed

Ohya Yoshinobu, Ishikawa Kenji, Komuro Tatsuya, Yamaguchi Tsuyoshi, Takeda Keigo, Kondo Hiroki, Sekine Makoto, Hori Masaru

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 50 ( 15 ) 2017.3

Behavior of absolute densities of atomic oxygen in the gas phase near an object surface in an AC-excited atmospheric pressure He plasma jet Reviewed

Takeda Keigo, Kumakura Takumi, Ishikawa Kenji, Tanaka Hiromasa, Sekine Makoto, Hori Masaru

APPLIED PHYSICS EXPRESS Vol. 10 ( 3 ) 2017.3

Characteristics of optical emissions of arc plasma processing for high-rate synthesis of highly crystalline single-walled carbon nanotubes Reviewed

Ando Atsushi, Takeda Keigo, Ohta Takayuki, Ito Masafumi, Hiramatsu Mineo, Ishikawa Kenji, Kondo Hiroki, Sekine Makoto, Suzuki Tomoko, Inoue Sakae, Ando Yoshinori, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 3 ) 2017.3

Investigation of effects of ion energies on both plasma-induced damage and surface morphologies and optimization of high-temperature Cl-2 plasma etching of GaN Reviewed

Liu Zecheng, Pan Jialin, Asano Atsuki, Ishikawa Kenji, Takeda Keigo, Kondo Hiroki, Oda Osamu, Sekine Makoto, Hori Masaru

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 56 ( 2 ) 2017.2

Absolute density of precursor SiH3 radicals and H atoms in H-2-diluted SiH4 gas plasma for deposition of microcrystalline silicon films Reviewed

Abe Yusuke, Ishikawa Kenji, Takeda Keigo, Tsutsumi Takayoshi, Fukushima Atsushi, Kondo Hiroki, Sekine Makoto, Hori Masaru

APPLIED PHYSICS LETTERS Vol. 110 ( 4 ) 2017.1

Thermal Cyclic Atomic-Level Etching of Nitride Films: A Novel Way for Atomic-Scale Nanofabrication Reviewed

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

ATOMIC LAYER DEPOSITION APPLICATIONS 13 Vol. 80 ( 3 ) page： 3 - 14 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：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 (NH4)2SiF6 layer on the SiNx surface. The second step is rapid thermal annealing with infrared (IR) irradiation to decompose and sublimate the (NH4)2SiF6 layer. Etching of SiNx was observed after the (NH4)2SiF6 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 SiC2 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