研究者詳細 - 石川　健治

論文 - 石川　健治

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

Ngo Quang Minh, Ngo Van Nong, Osamu Oda, Kenji Ishikawa, and Masaru Hori

Vacuum 224 巻頁： 113180 2024年6月

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

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

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

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

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

DOI： 10.1038/s41598-024-61501-9

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

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

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

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

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

DOI： 10.1116/6.0003432

Open Access

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

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

THIN SOLID FILMS 795 巻頁： 140322 2024年4月

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

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

DOI： 10.1016/j.tsf.2024.140322

Dissociative properties of C4F6 obtained using computational chemistry 査読有り Open Access

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

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

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

The electronic properties of C4F6 were investigated by using computational chemistry to clarify the dissociative channels in the process plasma. The results show the mainly ionized ion is C3F3+ (CF2=C=CF+; propargyl ion) which is observed in the mass spectrum with the electron energy of 70 eV, and the intermediate molecular structure to produce C3F3+ ion is methyl allene ion (CF2=C=CF-CF3+). The molecular ion C4F6+ is also mainly produced in the ionization threshold region. For the excited states, the calculated results suggest that CF2CFCF + CF2 dissociation takes place in the energy region higher than 7.0 eV and C2F3 + C2F3 dissociation takes place in the energy region higher than 8.0 eV. In the electron attachment process, the vertical electron attachment energy was calculated as 1.1 eV and the nonadiabatic negative ion energy was −0.2 eV lower than the energy of neutral C4F6

DOI： 10.35848/1347-4065/ad3166

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

Shu Tanaka, Sae Hayashi, Tomohiro Otsuka, Tetsuro Kamiya, Kenji Ishikawa, and Hirokazu Hara

Free Radical Research 58 巻 ( 3 ) 頁： 170 - 179 2024年3月

Plasma-driven sciences: Exploring complex interactions at plasma-boundaries 査読有り Open Access

Kenji Ishikawa, Kazunori Koga, and Noriyasu Ohno

Plasma 7 巻 ( 1 ) 頁： 160 - 177 2024年2月

液中プラズマによるナノグラフェンの高速合成と機能化査読有り Open Access

近藤博基, 堤隆義, 石川健治, 堀勝, 平松美根男

表面と真空 67 巻 ( 2 ) 頁： 77 - 82 2024年2月

Elaborate Cooperation of Poly(rC)-binding Proteins 1/2 and Glutathione in Ferroptosis Induced by Plasma-activated Ringer' s Lactate 査読有り 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 214 巻頁： 28 - 41 2024年2月

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

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

APPLIED SURFACE SCIENCE 645 巻頁： 158876 2024年2月

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

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

DOI： 10.1016/j.apsusc.2023.158876

Oxygen radical irradiation transforms an organic fertilizer l-tryptophan into an environment and human-friendly bactericide 査読有り 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 33 巻頁： 103496 2024年2月

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

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

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

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

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

DOI： 10.1016/j.radphyschem.2023.111304

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CiNii Research

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

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

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

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

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

DOI： 10.1007/978-3-031-62523-7_17

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

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

APPLIED SURFACE SCIENCE 638 巻頁： 157981 2023年11月

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

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

DOI： 10.1016/j.apsusc.2023.157981

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

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

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

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

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

DOI： 10.1063/5.0173553

Scopus

CiNii Research

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

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

Japanese Journal of Applied Physics 62 巻 ( SN ) 頁： SN1019 2023年11月

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

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

Plasma Processes and Polymers 20 巻 ( 11 ) 頁： 1 - 5 2023年11月

低温プラズマおよびハイパーサーミア併用効果を用いたがん治療の可能性招待有り査読有り

近藤隆, 橋爪博司, 田中宏昌, 石川健治, 齋藤淳一, 堀勝

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

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

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

DOI： 10.3191/thermalmed.39.21

CiNii Research

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

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

Japanese Journal of Applied Physics 62 巻 ( SL ) 2023年9月

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

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

DOI： 10.35848/1347-4065/acd4ca

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

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

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

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

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

DOI： 10.1002/ppap.202200193

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論文 - 石川 健治

<石川　健治>

論文 - 石川　健治