研究者詳細 - 石丸　学

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第12回ミクロ・ナノ解析に関する日本・ポーランド合同セミナー開催報告査読有り

石丸学

まてりあ ( 公益社団法人日本金属学会 ) 57 ( 12 ) 631 - 631 2018年01月

Proton-Driven Intercalation and Ion Substitution Utilizing Solid-State Electrochemical Reaction 査読有り

Fujioka M., Wu C., Kubo N., Zhao G., Inoishi A., Okada S., Demura S., Sakata H., Ishimaru M., Kaiju H., Nishii J.

Journal of the American Chemical Society 139 ( 49 ) 17987 - 17993 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 American Chemical Society. The development of an unconventional synthesis method has a large potential to drastically advance materials science. In this research, a new synthesis method based on a solid-state electrochemical reaction was demonstrated, which can be made available for intercalation and ion substitution. It was referred to as proton-driven ion introduction (PDII). The protons generated by the electrolytic dissociation of hydrogen drive other monovalent cations along a high electric field in the solid state. Utilizing this mechanism, Li + , Na + , K + , Cu + , and Ag + were intercalated into a layered TaS 2 single crystal while maintaining high crystallinity. This liquid-free process of ion introduction allows the application of high voltage around several kilovolts to the sample. Such a high electric field strongly accelerates ion substitution. Actually, compared to conventional solid-state reaction, PDII introduced 15 times the amount of K into Na super ionic conductor (NASICON)-structured Na 3-x K x V 2 (PO 4 ) 3 . The obtained materials exhibited a thermodynamically metastable phase, which has not been reported so far. This concept and idea for ion introduction is expected to form new functional compounds and/or phases.

DOI： 10.1021/jacs.7b09328

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Helium Irradiation and Implantation Effects on the Structure of Amorphous Silicon Oxycarbide 査読有り

Su Q., Inoue S., Ishimaru M., Gigax J., Wang T., Ding H., Demkowicz M., Shao L., Nastasi M.

Scientific Reports 7 ( 1 ) 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 The Author(s). Despite recent interest in amorphous ceramics for a variety of nuclear applications, many details of their structure before and after irradiation/implantation remain unknown. Here we investigated the short-range order of amorphous silicon oxycarbide (SiOC) alloys by using the atomic pair-distribution function (PDF) obtained from electron diffraction. The PDF results show that the structure of SiOC alloys are nearly unchanged after both irradiation up to 30 dpa and He implantation up to 113 at%. TEM characterization shows no sign of crystallization, He bubble or void formation, or segregation in all irradiated samples. Irradiation results in a decreased number of Si-O bonds and an increased number of Si-C and C-O bonds. This study sheds light on the design of radiation-tolerant materials that do not experience helium swelling for advanced nuclear reactor applications.

DOI： 10.1038/s41598-017-04247-x

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Formation of metastable phases in Zr-ion-irradiated Al<inf>2</inf>O<inf>3</inf>upon thermal annealing 査読有り

Oka N., Ishimaru M., Tane M., Sina Y., McHargue C., Sickafus K., Alves E.

Microscopy 66 ( 6 ) 388 - 396 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© The Author 2017. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. Formation of metastable phases in Zr-ion-irradiated corundum alumina (Al 2 O 3 ) upon thermal annealing was examined using transmission electron microscopy. A metastable cubic spinel phase was formed in the topmost layer of the as-irradiated microstructure. During thermal annealing at temperatures ranging from 1073 to 1273 K, this spinel layer grew in extent via an unusual corundum-to-spinel phase transformation. A normal spinel-to-corundum phase transformation was observed at post-irradiation annealing temperatures greater than 1473 K. In addition, ZrO 2 nanocrystals embedded in α-Al 2 O 3 were observed to form at these higher temperatures. High-resolution transmission electron microscopy observations and electron diffraction experiments revealed that the structure of the ZrO 2 precipitates observed in this study are consistent with a highpressure metastable orthorhombic phase of ZrO 2 known as the Ortho-I phase.

DOI： 10.1093/jmicro/dfx028

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Low-temperature synthesis of crystalline GeSn with high Sn concentration by electron excitation effect 査読有り

Kimura T., Ishimaru M., Okugawa M., Nakamura R., Yasuda H.

Japanese Journal of Applied Physics 56 ( 10 ) 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 The Japan Society of Applied Physics. The low-temperature synthesis of high-Sn-concentration GeSn is challenging in realizing flexible thin-film transistors and solar cells. Because of athermal processes, irradiation with energetic particles is anticipated to significantly reduce the processing temperature for device fabrication. Here, we demonstrated that polycrystalline Ge with 30 at.% Sn can be realized at room temperature by the electron-beam-induced recrystallization of amorphous GeSn. We found that inelastic electronic stopping, the so-called electron excitation effect, plays an important role in the recrystallization of amorphous GeSn.

DOI： 10.7567/JJAP.56.100307

Kyutacar

Scopus

CiNii Article

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Inhomogeneous crystallization of sputter-deposited amorphous Ge films 査読有り

Nakamura R., Okugawa M., Ishimaru M., Yasuda H., Numakura H.

AM-FPD 2017 - 24th International Workshop on Active-Matrix Flatpanel Displays and Devices: TFT Technologies and FPD Materials, Proceedings 276 - 278 2017年08月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Crystallization of amorphous germanium films induced by electron irradiation was investigated by in-situ transmission electron microscopy under a low electron-eneigy of 125 keV with various pre-Aging treatments at room temperature. Different microstructures were observed depending on the aging time: coarse and spherical nanoparticles grew rapidly in samples aged for less than 3 months, while a homogeneous nanociystalline structure with a grain size of about 10 nm appealed in samples aged for over 7 months. Analyses by the pair distribution lunction revealed that the initial structure is inhomogeneous, consisting of a mixture of amorphous regions and some ordered arrangements, but turned spontaneously to homogeneous random amorphous structures during aging. Such inhomogeneity could be an origin of the rapid growth of nanoparticles in the samples not subjected to the long-Time aging.

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Strong c-axis correlated pinning and hybrid pinning in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-δ</inf> films containing BaHfO<inf>3</inf> nanorods and stacking faults 査読有り

Horide T., Otsubo K., Kita R., Matsukida N., Ishimaru M., Awaji S., Matsumoto K.

Superconductor Science and Technology 30 ( 7 ) 2017年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 IOP Publishing Ltd. High critical current density (J c ) was achieved in low temperatures of 40 and 20 K in YBa 2 Cu 3 O 7-δ films containing elongated BaHfO 3 nanorods and stacking faults, which were prepared using pulsed laser deposition and post-oxygen-annealing. The YBa 2 Cu 3 O 7-δ + BaHfO 3 film exhibited global pinning force maximum (F p,max ) of 312 GNm -3 at 40 K and 619 GNm -3 at 20 K due to strong pinning by nanorods. These Fp,max values are comparable to those in the previously-reported high-J c films with almost the same matching field. Thus, the present study demonstrated that YBa 2 Cu 3 O 7-δ superconducting matrix realized high J c in low temperatures like other REBa 2 Cu 3 O 7-δ (RE = Gd, Sm, (Gd, Y)). Furthermore, high J c was obtained also for magnetic field parallel to the ab-plane, indicating hybrid pinning of nanorods and stacking faults. Thus, the stacking faults significantly affected the J c properties in the YBa 2 Cu 3 O 7-δ films containing nanorods.The present film structure with strong c-axis correlated pinning and hybrid pinning is effective in simultaneous control of J c values and J c anisotropy in YBa 2 Cu 3 O 7-δ films.

DOI： 10.1088/1361-6668/aa70d3

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Pin potential effect on vortex pinning in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-δ</inf> films containing nanorods: Pin size effect and mixed pinning 査読有り

Horide T., Matsukida N., Ishimaru M., Kita R., Awaji S., Matsumoto K.

Applied Physics Letters 110 ( 5 ) 2017年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 Author(s).The pin size effect and mixed pinning of nanorods and matrix defects are discussed for YBa2Cu3O7-δ films containing nanorods. BaSnO3 nanorods with a diameter of 11 nm and BaHfO3 nanorods with a diameter of 7 nm were prepared, and critical current density (Jc) and resistivity were measured in the films. When the coherence length was larger than the nanorod size at high temperatures near the critical temperature, the trapping angle and activation energy of the vortex flow depended on the nanorod diameter. At a moderate temperature of 65−77 K, the pin size effect on Jc disappeared since the coherence length became smaller than the nanorod size. At a low temperature of 20 K, the contribution from matrix pinning became comparable to that of nanorods in a high magnetic field due to the small coherence length. Thus, the temperature-dependent coherence length caused the pin potential situation to vary significantly, namely, the pin size effect and mixed pinning, which strongly affected vortex pinning in YBa2Cu3O7-δ containing nanorods.

DOI： 10.1063/1.4975300

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アモルファスGeにおける構造緩和過程の分子動力学法による解析査読有り

Imabayashi S., Ishimaru M.

日本金属学会誌 81 ( 2 ) 66 - 70 2017年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

© 2016 The Japan Institute of Metals and Materials.Structural relaxation of amorphous germanium has been examined by molecular dynamics simulations based on the empirical Tersoff interatomic potential. Although the Tersoff potential overestimated both the melting and glass transition temperatures, it was found that this potential can reproduce the behavior of structural relaxation. The potential energy decreased with thermal annealing below the glass transition temperature, but it sometimes increased during structural relaxation. The mean square displacement of atoms also increased at the corresponding period. These changes were attributed to the cooperative atomic motion during structure relaxation. Atomic trajectories revealed that structural changes are induced by spatially- and temporally-inhomogeneous atomic motions: atomic mobile and immobile regions coexisted during structural relaxation.

DOI： 10.2320/jinstmet.J2016051

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CiNii Article

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Molecular dynamics study on structural relaxation processes in amorphous germanium 査読有り

Imabayashi S., Ishimaru M.

Materials Transactions 58 ( 6 ) 857 - 861 2017年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 The Japan Institute of Metals and Materials.The structural relaxation of amorphous germanium was examined by molecular dynamics simulations based on the empirical Tersoff interatomic potential. Although the Tersoff potential overestimated both the melting and glass transition temperatures, it was able to reproduce the structural relaxation behavior. The potential energy decreases with thermal annealing below the glass transition temperature, but occasionally increases during structural relaxation. The mean square displacement of atoms also increases in these periods. These changes were attributed to cooperative atomic motion during the structural relaxation. Atomic trajectories revealed that structural changes are induced by spatially- and temporally-inhomogeneous atomic motions: atomically mobile and immobile regions coexist during structural relaxation.

DOI： 10.2320/matertrans.M2017036

Scopus

CiNii Article

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透過電子顕微鏡法による照射誘起構造変化の解析招待有り査読有り

石丸学

顕微鏡 ( 公益社団法人日本顕微鏡学会 ) 52 ( 1 ) 24 - 28 2017年01月

担当区分：筆頭著者記述言語：日本語掲載種別：記事・総説・解説・論説等（学術雑誌）

<p>照射場を利用した材料創製では，通常の手法では得ることが難しい平衡状態から離れた準安定構造を実現することが出来る．また，機能性材料および構造用材料の照射誘起構造変化に関する研究は，宇宙空間や原子炉等の極限環境下で使用される材料の信頼性を知る上で重要である．本稿では，照射場と材料の相互作用による構造変化およびそれを利用した材料創製に関する最近の研究成果について報告する．準安定構造の形成に関しては，イオン照射アルミナの熱処理過程において見出された，通常の熱処理では起こらないコランダム→スピネル型構造相変態について報告する．一方，耐照射性材料の開発に関する一連の研究では，ナノ構造制御により炭化ケイ素の耐照射性を向上させた例について紹介する．</p>

DOI： 10.11410/kenbikyo.52.1_24

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130007689241

Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations 査読有り

R. Takase, M. Ishimaru, N. Uchida, T. Maeda, K. Sato, R. R. Lieten, J.-P. Locquet

Journal of Applied Physics 120 245304(1) - 245304(9) 2016年12月

Thermal crystallization of sputter-deposited amorphous Ge films: Competition of diamond cubic and hexagonal phases 査読有り

M. Okugawa, R. Nakamura, M. Ishimaru, H. Yasuda, H. Numakura

AIP Advances 6 125035(1) - 125035(9) 2016年12月

Crystallization of sputter-deposited amorphous Ge films by electron irradiation: Effect of low-flux pre-irradiation 査読有り

M. Okugawa, R. Nakamura, M. Ishimaru, H. Yasuda, H. Numakura

Journal of Applied Physics 120 134308(1) - 134308(7) 2016年10月

Discovery of Pt based superconductor LaPt5As 査読有り

M. Fujioka, M. Ishimaru, T. Shibuya, Y. Kamihara, C. Tabata, H. Amitsuka, A. Miura, M. Tanaka, Y. Takano, H. Kaiju, J. Nishi

Journal of the American Chemical Society 138 9927 - 9934 2016年07月

Role of nanoscale precipitates for enhancement of thermoelectric properties of heavily P-doped Si-Ge alloys 査読有り

A. Yusufu, K. Kurosaki, Y. Miyazaki, M. Ishimaru, A. Kosuga, Y. Ohishi, H. Muta, and S. Yamanaka

Materials Transactions 57 1070 - 1075 2016年06月

Amorphization resistance of nano-engineered SiC under heavy ion irradiation 査読有り

K. Imada, M. Ishimaru, H. Xue, Y. Zhang, S. Shannon, and W. J. Weber

Journal of Nuclear Materials 478 310 - 314 2016年06月

Structural transition in sputter-deposited amorphous germanium films by aging at ambient temperature 査読有り

M. Okugawa, R. Nakamura, M. Ishimaru, K. Watanabe, H. Yasuda, and H. Numakura

Journal of Applied Physics 119 214309(1) - 214309(7) 2016年05月

Influence of matching field on critical current density and irreversibility temperature in YBa2Cu3O7 films with BaMO3 (M=Zr, Sn, Hf) nanorods 査読有り

T. Horide, K. Taguchi, K. Matsumoto, N. Matsukida, M. Ishimaru, P. Mele, R. Kita

Applied Physics Letters 108 082601(1) - 082601(5) 2016年01月

Carrier and heat transport properties of polycrystalline GeSn films on SiO2 査読有り

M. Uchida, T. Maeda, R. R. Lieten, S. Okajima, Y. Ohishi, R. Takase, M. Ishimaru, J.-P. Locquet

Applied Physics Letters 2015年12月

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