記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jpcs.2022.111114

Web of Science

Scopus

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.actamat.2023.118738

Web of Science

Scopus

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 Review Materials  

It was experimentally reported that II-VI group inorganic semiconductor crystals become harder and brittle by external light illumination. In order to reveal essential factors of the light illumination effect, systematic GGA+U calculations are performed for 30° partial dislocations in ZnSe and ZnTe, and the obtained results are discussed together with those for ZnS reported previously. It is found in these three crystal systems that the cores of pristine partial dislocations have unreconstructed atomic structures whereas their cores undergo atomic reconstruction energetically more favorably by trapping excess carriers. Such carrier trapping and atomic reconstruction of the dislocation cores are ascribed to the presence of excess electrostatic potentials at the cores due to ionic bonding characters of the host crystals. The dislocation core reconstructions decrease potential energies of the partial dislocations and can in turn increase Peierls-potential barriers for dislocation glide, corresponding to the observed hardening and brittleness by light illumination. The energy gains due to the dislocation-core reconstructions also depend on energy positions of the defect-induced levels that appear within the band gaps.

DOI： 10.1103/PhysRevMaterials.7.013603

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Scopus

記述言語：日本語   出版者・発行元：公益社団法人 日本金属学会  

DOI： 10.2320/materia.61.629

CiNii Research

記述言語：日本語   出版者・発行元：公益社団法人 日本顕微鏡学会  

<p>近年，脆く壊れやすいと考えられていた半導体材料が室温でも高い可塑性を示しうることが明らかとなっている．例えば，チタン酸ストロンチウム（SrTiO₃）結晶では，点欠陥濃度を制御することで室温での塑性変形能（可塑性）が向上する．また，硫化亜鉛（ZnS）結晶では，光照射下では壊れやすいが，暗闇の中では大きな可塑性を発現する．このように従来想像すらされていなかった結晶の異常な可塑性が見出され，大きく注目を集めている．これら半導体ともセラミックスとも言える材料系は，脆いがゆえに構造材としての適正がなく，結果として専ら機能材料として利用されてきた．材料の脆さを克服できるメカニズムが見つかれば，そのメカニズムの理解は様々な材料系にとって非常に有用であり，構造材として利用できる材料系の拡大が期待される．本稿では，結晶の形状変化のその場観察および電子顕微鏡による転位組織観察を元に，SrTiO₃よびZnSの可塑性向上に関する最新の研究を議論する．</p>

DOI： 10.11410/kenbikyo.56.3_110

CiNii Research

記述言語：日本語   出版者・発行元：一般社団法人 粉体粉末冶金協会  

The science and technology related with light has revolutionized modern society, and understanding the effects of light on semiconducting materials has become crucial to current science and technology. Although much research has been done on the effects of light on the electronic and optical properties of materials, the effects of light on the mechanical properties of materials are not well understood. It was recently found that extraordinarily large plasticity appears in bulk compression of single-crystal ZnS in complete darkness even at room-temperature. This is believed to be due to the less interactions between dislocations and photo-excited electrons and/or holes. However, methods for evaluating dislocation behavior in such semiconductors with small dimensions under a particular light condition had not been well established. Here we show a new nanoindentation method that incorporates well designed lighting system for exploring dislocation behavior depending on the light conditions in advanced semiconductors. We used single-crystal ZnS as a model material because its bulk deformation behavior has been well investigated. It is confirmed that the decrease of dislocation mobility with light observed in conventional bulk deformation tests can be understood even by the nanoindentation tests at room-temperature. It is remarkable that we experimentally demonstrate that dislocation mobility appears to be more sensitive to light exposure than dislocation nucleation.

DOI： 10.2497/jjspm.68.469

Scopus

CiNii Research

記述言語：日本語   出版者・発行元：Applied Physics Letters  

An enormous change in the dislocation-mediated plasticity has been found in a bulk semiconductor that exhibits the photoplastic effect. Herein, we report that UV (365 nm) light irradiation during mechanical testing dramatically decreases the fracture toughness of ZnS. The crack tip toughness on a (001) single-crystal ZnS, as measured by the near-tip crack opening displacement method, is increased by ∼45% in complete darkness compared to that in UV light. The increase in fracture toughness is attributed to a significant increase in the dislocation mobility in darkness, as explained by the crack tip dislocation shielding model. Our finding suggests a route toward controlling the fracture toughness of photoplastic semiconductors by tuning the light irradiation.

DOI： 10.1063/5.0047306

Web of Science

Scopus

記述言語：日本語   出版者・発行元：Nano Letters  

It was recently found that extremely large plasticity is exhibited in bulk compression of single-crystal ZnS in complete darkness. Such effects are believed to be caused by the interactions between dislocations and photoexcited electrons and/or holes. However, methods for evaluating dislocation behavior in such semiconductors with small dimensions under a particular light condition had not been well established. Here, we propose the "photoindentation"technique to solve this issue by combining nanoscale indentation tests with a fully controlled lighting system. The quantitative data analyses based on this photoindentation approach successfully demonstrate that the first pop-in stress indicating dislocation nucleation near the surface of ZnS clearly increases by light irradiation. Additionally, the room-temperature indentation creep tests show a drastic reduction of the dislocation mobility under light. Our approach demonstrates great potential in understanding the light effects on dislocation nucleation and mobility at the nanoscale, as most advanced technology-related semiconductors are limited in dimensions.

DOI： 10.1021/acs.nanolett.0c04337

Web of Science

Scopus

PubMed

記述言語：日本語   出版者・発行元：公益社団法人 応用物理学会  

<p>光環境が半導体材料の電気的性質に影響することは広く知られているが，力学的性質にどのような影響があるかはあまり理解されていなかった．筆者らは最近，無機半導体の1つである硫化亜鉛（ZnS）結晶が，暗闇下であれば室温でも金属並みの可塑性（変形能，柔軟性）を示すことを発見した．暗闇下における塑性変形量は塑性ひずみ量45%に達しており，無機半導体はもろいというこれまでの常識を覆すものだった．興味深いことに，暗闇下で塑性変形を受けたZnS結晶はもともと大きくバンドギャップが変化し，従来知られていなかった新奇な光物性を示すことも明らかになりつつある．このような物性の変化は，変形により導入された金属並みの高密度な転位が無機半導体中に特異な電子構造を形成していることによる．つまり，従来は悪者にすぎなかった結晶欠陥の転位を逆に有効利用することで，新奇な半導体物性の開拓が可能となると期待される．</p>

DOI： 10.11470/oubutsu.90.3_176

CiNii Research

記述言語：日本語   出版者・発行元：公益社団法人 日本金属学会  

DOI： 10.2320/materia.60.30

CiNii Research