Faculty Profiles - ISHIKAWA, Kenji

Papers - ISHIKAWA, Kenji

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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

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

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

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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

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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

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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

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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

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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.

Scopus

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.

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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

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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

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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

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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

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

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

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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

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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

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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

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PubMed

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

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

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

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Papers - ISHIKAWA, Kenji