Faculty Profiles - ISHIKAWA, Kenji

Papers - ISHIKAWA, Kenji

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石川健治，堀勝

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

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

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

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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

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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

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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

Open Access

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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

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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

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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

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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

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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

Insights into normothermic treatment with direct irradiation of atmospheric pressure plasma for biological applications Reviewed

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

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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

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Papers - ISHIKAWA, Kenji