研究者詳細 - 石川　健治

論文 - 石川　健治

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

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

VACUUM 205 巻 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Vacuum

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

DOI： 10.1016/j.vacuum.2022.111351

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

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

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

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

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

DOI： 10.35848/1347-4065/ac895e

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

紅林佑弥, 石川健治, 田中宏昌, 秋山真一, 橋爪博司, 堀勝

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

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

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

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

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

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

DOI： 10.1002/ppap.202100203

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

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

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/O<sub>2</sub>/C<sub>4</sub>F<sub>8</sub> plasma etching process 査読有り

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

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

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

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

DOI： 10.1039/d2cp00289b

Low-temperature reduction of SnO<sub>2</sub> by floating wire-assisted medium-pressure H<sub>2</sub>/Ar plasma 査読有り

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

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

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

Reduction of SnO<inf>2</inf> to form spherical Sn particles and Sn etching are obtained by floating wire (FW)-assisted medium-pressure H<inf>2</inf>/Ar plasma. High-density H<inf>2</inf>/Ar plasma (10<sup>14</sup> cm<sup>−3</sup>) with a larger treatment area at medium pressure (10 kPa) produces a two-times higher removal rate of SnO<inf>2</inf> (0.111 mg/min) than that at atmospheric pressure with the same treatment area of 300 mm<sup>2</sup>. SnO<inf>2</inf> film is removed from the glass surface by a two-step process involving (1) reduction of SnO<inf>2</inf> by FW-H<inf>2</inf>/Ar plasma to form spherical Sn particles and (2) removal of low-contact Sn particles by water-based cleaning. High surface smoothness (roughness of 0.488 nm) and high optical transmittance (>92%) of treated samples indicate no damage compared to that of pristine quartz glass.

DOI： 10.1002/ppap.202100209

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

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

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

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

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

DOI： 10.35848/1882-0786/ac6360

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

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

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

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

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

DOI： 10.1116/6.0001660

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

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

AIP ADVANCES 12 巻 ( 2 ) 2022年2月

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

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

DOI： 10.1063/5.0075530

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

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

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

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

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

DOI： 10.35848/1347-4065/ac2037

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

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

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

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

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

DOI： 10.35848/1347-4065/ac1c3d

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

Ishikawa, K

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

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

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

DOI： 10.35848/1347-4065/ac3558

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

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

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

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

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

DOI： 10.35848/1347-4065/ac25dc

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

Takeda, K; Ishikawa, K; Hori, M

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

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

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

DOI： 10.1007/s41614-022-00075-3

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

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

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

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

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

DOI： 10.1109/ISSM55802.2022.10027112

On the Etching Mechanism of Highly Hydrogenated SiN Films by CF<sub>4</sub>/D<sub>2</sub> Plasma: Comparison with CF<sub>4</sub>/H<sub>2</sub> 査読有り Open Access

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

COATINGS 11 巻 ( 12 ) 頁： 1535 2021年12月

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

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

DOI： 10.3390/coatings11121535

プラズマがん治療招待有り査読有り

石川健治，堀勝

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

Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF<sub>4</sub>/H<sub>2</sub> plasma at different substrate temperatures 査読有り

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

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

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

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

DOI： 10.1002/ppap.202100078

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

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

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

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

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

DOI： 10.1002/ppap.202100056

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