研究者詳細 - 大野　哲靖

論文 - 大野　哲靖

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Lithography-Free Nanofabrication on Various Semiconductors by the Codeposition Etching Technique 査読有り国際誌

Shi Q., Kajita S., Ohno N., Tanaka H., Yasuhara R., Fujiwara H., Uehara H.

Langmuir 40 巻 ( 24 ) 頁： 12437 - 12442 2024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：Langmuir

Nano-/microstructures can be formed with the aid of small amounts of impurities during deposition with noble gas plasma irradiation, which is referred to as codeposition etching. This can be a new method for lithography-free semiconductor nanofabrication. Here, the codeposition etching method was employed with argon plasma and molybdenum (Mo) impurities on various semiconductors. Structures can be formed only on substrates that have a lower sputtering yield than the seed impurity. The density, area, and height of structures are related to both the impurity deposition rate and the substrate material. Moreover, two mechanisms of impurity nucleation are proposed according to time dependence results for the formation of the structures.

DOI： 10.1021/acs.langmuir.4c00686

Scopus

PubMed

First results of multi-fluid modeling of detached hydrogen plasmas in a linear plasma device using fluid code LINDA-NU 査読有り国際誌

Sugiura K., Ido T., Tanaka H., Natsume H., Masuda S., Hoshino K., Sawada K., Ohno N.

Contributions to Plasma Physics 2024;e202300150 巻 2024年6月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Contributions to Plasma Physics

In order to simulate hydrogen (H) plasma in the linear plasma device NAGDIS-II, we have modified the fluid code LINDA-NU to allow the simultaneous calculation of multiple ion species consisting of hydrogen atomic ions ((Formula presented.)) and molecular ions ((Formula presented.)). In this simulation, H and (Formula presented.) neutrals are assumed to be uniformly distributed in space in order to obtain initial qualitative results. The fraction of (Formula presented.) ions increases as the (Formula presented.) molecular density increases, and the recombination process between (Formula presented.) and electrons is observed to reduce the particle flux to the target plate. With an increase in H density, the electron density increases due to the decrease in ion flow velocity due to the change exchange process, and the electron temperature decreases to less than 1 eV, leading to the detached plasma formation attributed to the electron-ion recombination process.

DOI： 10.1002/ctpp.202300150

Scopus

Four-dimensional conditional averaging tomography of rotating plasma ejection from cylindrical detached plasma 査読有り国際誌

Tanaka H., Kajita S., Natsume H., Ohno N.

Scientific Reports 14 巻 ( 1 ) 頁： 9329 2024年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Detached plasma formation is a way to reduce the heat load on the wall in magnetic fusion devices. This study proposes a novel analysis technique consisting of the conditional averaging, sliding window, and tomography to reveal the spatiotemporal behavior of the rotating radial ejection event of detached plasma, which further contributes to local heat load reduction. The used equipment is a high-speed camera and an electrostatic probe located at the periphery of the linear plasma device NAGDIS-II. By applying this method, four-dimensional (4D) behavior of the emission structure along time (1D) and space perpendicular and parallel to the magnetic field (3D) was clarified; a rotating distorted structure appears as a precursor, which is then scraped and transported radially and axially. The proposed method is widely applicable to short-term rigid-body rotating structures, especially in linear plasmas.

DOI： 10.1038/s41598-024-59182-5

Scopus

PubMed

Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX 招待有り査読有り

H.Tanaka, N.Ezumi, T.Sugiyama, H.Gamo, N.Shigematsu, M.Yoshikawa, J.Kohagura, M.Hirata, S.Togo N.Ohno, M.Sakamoto

Physics of Plasmas 30 巻 ( 3 ) 頁： 10.1063/5.0129886 2023年3月

Increased Photoelectrochemical Performance of Vanadium Oxide Thin Film by Helium Plasma Treatment with Auxiliary Molybdenum Deposition 査読有り国際共著

Kajita Shin, Eda Tomoki, Feng Shuangyuan, Tanaka Hirohiko, Bieberle-Hutter Anja, Ohno Noriyasu

ADVANCED ENERGY AND SUSTAINABILITY RESEARCH 4 巻頁： 2200141 2023年1月

Structural correlation of random lasing performance in plasma-induced surface-modified galium nitride 査読有り

Q.Shi, H.Fujiwara, S.Kajita, R.Yasuhara H.Tanaka, N.Ohno,H.Uehara

ACS Applied Optical Materials 1 巻頁： 412 - 420 2022年12月

Corrigendum to “Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide” [Appl. Surf. Sci. 580 (2022) 151979] (Applied Surface Science (2022) 580, (S0169433221030166), (10.1016/j.apsusc.2021.151979)) 招待有り査読有り

S.Feng, S.Kajita, M.Higashi, A.Bieberle-Hutter, T.Yoshida, N.Ohno

Applied Surface Science 599 巻頁： 153668 2022年10月

Reduction of pulsed particle load with dynamic pressure induced by transient recycled neutral flux 査読有り国際共著国際誌

Hayashi Y., Tanaka H., Ohno N., Kajita S., Morgan T., van der Meiden H., Scholten J., Vernimmen J., Natsume H., Sawada K., Masuda S.

Plasma Physics and Controlled Fusion 64 巻 ( 10 ) 頁： 105013 2022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：Plasma Physics and Controlled Fusion

From pulsed plasma experiments focusing on neutral pressure dependence, the impacts of a transition from a low to a high recycling target on the particle load were investigated and discussed in the linear plasma device, Magnum-PSI. Time traces of the target ion flux were mitigated in high neutral pressure cases because of a plasma-neutral interaction. On the other hand, in low neutral-pressure cases, the target ion flux indicated partial suppression in the last part of the pulse. The Langmuir probe, located 200 mm upstream from the target plate, did not exhibit such a suppression. Pulse suppression can be expected from the localized interaction between recycled neutral flux and pulsed plasma in front of the target. The mean-free paths of recycled neutral particles regarding the charge exchange with pulse ions and elastic scattering with background neutral particles were compared. Modeling using a fluid code coupled with a neutral transport code was performed, and it was concluded that dynamic pressure induced by the transient recycled neutral flux caused sufficient momentum loss to stagnate the pulsed plasma toward the target plate.

DOI： 10.1088/1361-6587/ac8acb

Scopus

Bidirectional reflectance distribution function of recrystallized tungsten mono-block exposed to cyclic heat loading 査読有り国際誌

Natsume H., Nojiri K., Kajita S., Fukuda M., Ushiki T., Tanaka H., Sugie T., Kitazawa S.i., Kikuchi T., Yokozuka T., Ohno N., Ezato K., Hatae T.

Nuclear Materials and Energy 33 巻頁： 101243 2022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：Nuclear Materials and Energy

The bidirectional reflectance distribution function (BRDF) of recrystallized tungsten mono-blocks exposed to cyclic heat loading for ITER divertor outer vertical target was measured using a goniophotometer at a wavelength of 473 nm. Laser microscope observations revealed that the surface roughness of the mono-block increased by an order of magnitude after cyclic heat loads of approximately 20 MWm−2. Furthermore, the overall values of BRDF decreased with an increase in cyclic heat loading. A comparison between the modeled and measured BRDFs showed that an additional Lambertian component is necessary to a specular function (microfacet model or Gaussian function) to fit the measured BRDFs when the surface of the mono-blocks becomes rough.

DOI： 10.1016/j.nme.2022.101243

Scopus

Fuzz Growth Process under He-W Co-Deposition Conditions 査読有り国際共著国際誌

Shen W., Kajita S., Tanaka H., Shi Q., Ohno N.

Plasma and Fusion Research 17 巻 ( 0 ) 頁： 1302094 - 1302094 2022年8月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人プラズマ・核融合学会

Helium (He)-Tungsten (W) co-deposition experiments were conducted in the linear plasma device Co-NAGDIS at a temperature of 1223K to observe the characteristics of fuzz growth on theWsurface with auxiliary W deposition. The dependence on the deposition rate of W was investigated and a clear difference in fuzz thickness was found between He-only and co-deposition experiments. In addition, the fuzz structures on a single sample exhibited a spatially nonuniform distribution, which was probably caused by the nonuniformity in the deposition rate.

DOI： 10.1585/pfr.17.1302094

Scopus

CiNii Research

Measurement of the Bidirectional Reflectance Distribution Function of Tungsten Surface Sputtered in Argon Plasma 査読有り

H.Natsume, K.Nojiri, S.Kajita, T.Ushiki, T.Sugie, S.Kitazawa, T.Kikuchi, T.Yokozuka, H.Tanaka, N.Ohno, T.Hatae

Plasma and Fusion Research:Regular Articles 17 巻頁： 2405041 2022年5月

Isotope Effect for Plasma Detachment in Helium and Hydrogen/Deuterium Mixture Plasmas 査読有り国際誌

Guo X., Tanaka H., Kajita S., Ohno N., Hattori S., Sawada K.

Plasma and Fusion Research 17 巻 ( 0 ) 頁： 2402027 - 2402027 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：一般社団法人プラズマ・核融合学会

To investigate the isotope effect on the plasma detachment in helium (He) and hydrogen (H)/deuterium (D) mixture plasmas, we performed H2, D2 or He gas puffing into He plasma in the linear plasma device NAGDIS-II. Axial distributions of electron density (ne) and electron temperature (Te) were obtained using a movable Langmuir probe. Additionally, optical emission spectroscopy (OES) was applied to measure axial distributions of Balmer lines and He I lines. When the neutral gas pressure was high (ΔPn = 7~10 mTorr), ne distribution in He-D2 mixture plasma was similar to that in pure He plasma, showing a sharp decrease at the downstream region where Te < 1 eV. In contrast, in He-H2 mixture plasma, a decrease in ne was confirmed from upstream region where Te > 1 eV. The upstream Hα/Hγ in He-H2 plasma was significantly larger than the Dα/Dγ in He-D2 plasma at the same Te. This result indicated that molecular activated recombination (MAR) processes significantly occurred in He-H2 plasma, while electron-ion recombination (EIR) processes were dominant in He-D2 and pure He plasmas.

DOI： 10.1585/pfr.17.2402027

Scopus

CiNii Research

Study of optical emission spectroscopy in dual frequency synchronized pulsed capacitively coupled discharges with DC bias at low-pressure in Ar/O2/C4F8 plasma etching 査読有り国際共著

B.B,Sahu, K.Nakane, K.Ishikawa, M.Sekine, T.Tsutsumi, T.Gohira, Y.Ohya, N.Ohno, M.Hori

Physical Chemistry Chemical Physics 24 巻頁： 13883 - 13896 2022年5月

Changes in morphology and field emission property of nano-tendril bundles after high temperature annealing 査読有り国際共著国際誌

Zhang R., Kajita S., Hwangbo D., Sinelnikov D., Tanaka H., Ohno N.

Nuclear Materials and Energy 31 巻頁： 101178 2022年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Nuclear Materials and Energy

Nano-tendril bundles (NTBs) are known to be formed on tungsten by helium plasma exposure with additional neon impurity gas. In this study, the annealing experiments were conducted at the sample temperature of 1473 – 1673 K to investigate the changes of morphology and field emission property of NTBs. With NTBs formed on a W surface, the surface did not fully recover to a smoothed surface and the NTBs remained the fiber-form structures after the annealing at 1673 K for one hour. In addition, the onset electric field for field emission increased, while the emission current from NTBs significantly decreased after the annealing. When the samples were biased at −250 V during helium plasma exposure, arc ignition was confirmed on W surface with NTBs, whereas no arc ignition appeared on W with annealed NTBs.

DOI： 10.1016/j.nme.2022.101178

Scopus

An approach to implement a heat flux limit in a model for fusion relevant plasmas 査読有り国際共著

M.Z.Tokar, M.Kobayashi, N.Ohno

Physics of Plasmas 29 巻頁： 32502 2022年3月

Completion of JT-60SA construction and contribution to ITER 査読有り国際共著国際誌

Kamada Y., Di Pietro E., Hanada M., Barabaschi P., Ide S., Davis S., Yoshida M., Giruzzi G., Sozzi C., Abdel Maksoud W., Abe H., Aiba N., Akiyama T., Ayllon-Guerola J., Arai T., Artaud J.F., Asakura N., Ashikawa N., Balbinot L., Bando T., Baulaigue O., Belonohy E., Bin W., Bombarda F., Bolzonella T., Bonne F., Bonotto M., Botija J., Cabrera-Pérez S., Cardella A., Carraro L., Cavalier J., Chernyshova M., Chiba S., Clement-Lorenzo S., Cocilovo V., Coda S., Coelho R., Coffey I., Collin B., Corato V., Cucchiaro A., Czarski T., Dairaku M., Davis S., Day C., de la Luna E., De Tommasi G., Decool P., Di Pace L., Di Pietro E., Dibon M., Disset G., Ejiri A., Endo Y., Ezumi N., Falchetto G., Fassina A., Fejoz P., Ferro A., Fietz W., Figini L., Fornal T., Frello G., Fujita T., Fukuda T., Fukui K., Fukumoto M., Furukawa M., Futatani S., Gabellieri L., Gaio E., Galazka K., Garcia J., Garcia-Dominguez J., Garcia-Lopez J., Garcia-Munoz M., Garzotti L., Gasparini F., Gharafi S., Giacomelli L., Ginoulhiac G., Giruzzi G., Giudicotti L., Guillén González R., Hajnal N., Hall S., Hamada K., Hanada K., Hanada M., Hasegawa K., Hatae T., Hatakeyama S., Hauer V., Hayashi N., Hayashi T., Heller R., Higashijima S., Hinata J.

Nuclear Fusion 62 巻 ( 4 ) 頁： 42002 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：Nuclear Fusion

Construction of the JT-60SA tokamak was completed on schedule in March 2020. Manufacture and assembly of all the main tokamak components satisfied technical requirements, including dimensional accuracy and functional performances. Development of the plasma heating systems and diagnostics have also progressed, including the demonstration of the favourable electron cyclotron range of frequency (ECRF) transmission at multiple frequencies and the achievement of long sustainment of a high-energy intense negative ion beam. Development of all the tokamak operation control systems has been completed, together with an improved plasma equilibrium control scheme suitable for superconducting tokamaks including ITER. For preparation of the tokamak operation, plasma discharge scenarios have been established using this advanced equilibrium controller. Individual commissioning of the cryogenic system and the power supply system confirmed that these systems satisfy design requirements including operational schemes contributing directly to ITER, such as active control of heat load fluctuation of the cryoplant, which is essential for dynamic operation in superconducting tokamaks. The integrated commissioning (IC) is started by vacuum pumping of the vacuum vessel and cryostat, and then moved to cool-down of the tokamak and coil excitation tests. Transition to the super-conducting state was confirmed for all the TF, EF and CS coils. The TF coil current successfully reached 25.7 kA, which is the nominal operating current of the TF coil. For this nominal toroidal field of 2.25 T, ECRF was applied and an ECRF plasma was created. The IC was, however, suspended by an incident of over current of one of the superconducting equilibrium field coil and He leakage caused by insufficient voltage holding capability at a terminal joint of the coil. The unique importance of JT-60SA for H-mode and high-β steady-state plasma research has been confirmed using advanced integrated modellings. These experiences of assembly, IC and plasma operation of JT-60SA contribute to ITER risk mitigation and efficient implementation of ITER operation.

DOI： 10.1088/1741-4326/ac10e7

Scopus

Nitrogen Atom Density Measurements in NAGDIS-T Using Vacuum Ultraviolet Absorption Spectroscopy 査読有り

Nishio Ryosuke, Kajita Shin, Tanaka Hirohiko, Asaoka Koji, Tsutsumi Takayoshi, Hori Masaru, Ohno Noriyasu

PLASMA AND FUSION RESEARCH 17 巻 ( 0 ) 頁： 1201004 - 1201004 2022年1月

Plasma induced surface nanostructure on semiconductors for the application of random laser 査読有り

Shi Q., Fujiwara H., Osaka R., Kajita S., Yasuhara R., Ohno N., Uehara H.

Optics InfoBase Conference Papers 2022年

Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide 査読有り国際共著国際誌

Feng S., Kajita S., Higashi M., Bieberle-Hütter A., Yoshida T., Ohno N.

Applied Surface Science 580 巻頁： 151979(7 pp) 2021年12月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Surface Science

Helium (He)-induced nanostructured tungsten sheets were synthesized by He plasma irradiation under different plasma exposure durations. After calcination, nanostructured tungsten oxide samples were used as photoelectrodes to test photoelectrochemical (PEC) performance. The results showed that nanostructured WO3 photoanodes have higher PEC performance compared to the sample without nanostructures. The 15 min irradiated sample had the highest photocurrent density of 3.5 mA/cm2 under the thermodynamic potential of water oxidation (1.23 V vs. RHE). It was found that the oxide layer thickness and exposed crystal facet have a significant impact on PEC performance. The plasma synthesis technique has proved to be an effective method for preparing nanostructured WO3 photoelectrodes.

DOI： 10.1016/j.apsusc.2021.151979

Scopus

Growth of Mo Large-Scale Fiberform Nanostructures 査読有り

Kajita Shin, Okuyama Tatsuki, Tanaka Hirohiko, Ohno Noriyasu

PLASMA AND FUSION RESEARCH 16 巻 ( 0 ) 頁： 1206105 - 1206105 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：一般社団法人プラズマ・核融合学会

<p>We performed helium (He) plasma irradiation to molybdenum (Mo) substrate with auxiliary Mo deposition. Different from W cases, large-scale fiberform nanostructure (LFN) growth did not occur easily. The experiments suggested that the experimental condition of Mo LFN growth has a much narrower conditional window than that of fuzz growth or another hidden control factor exists for LFN growth.</p>

DOI： 10.1585/pfr.16.1206105

Web of Science

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