Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jpcs.2022.111114

Web of Science

Scopus

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.actamat.2023.118738

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevMaterials.7.013603

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Language：Japanese   Publisher：The Japan Institute of Metals and Materials  

DOI： 10.2320/materia.61.629

CiNii Research

Language：Japanese   Publisher：The Japanese Society of Microscopy  

<p>In recent years, it was reported that semiconductor materials, which were regarded to be brittle, can exhibit high plasticity even at room temperature. For example, in strontium titanate crystals, room-temperature plasticity can be improved by controlling the ratio of the constituent elements. In addition, zinc sulfide crystals are brittle under light irradiation, but show high plasticity in the dark. These unusual plasticity of semiconductor crystals, which had not even been imagined before, has attracted a great deal of attention. These “brittle” materials were not suitable as structural materials before, and consequently have been used exclusively as functional materials. However, the understanding of the mechanisms that can overcome the brittleness of these materials is very useful for various material systems, and the wider application of materials are expected. Here we discuss the recent studies on the improvement of the plasticity of strontium titanate and zinc sulfide based on the in-situ observation of the samples and TEM observations of the dislocation substructures.</p>

DOI： 10.11410/kenbikyo.56.3_110

CiNii Research

Language：Japanese   Publisher：Japan Society of Powder and Powder Metallurgy  

<p>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.</p>

DOI： 10.2497/jjspm.68.469

Scopus

CiNii Research

Language：Japanese   Publisher：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

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Language：Japanese   Publisher：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

Language：Japanese   Publisher：The Japan Society of Applied Physics  

<p>Inorganic semiconductors tend to fail in a brittle manner when subjected to an external force. Such poor mechanical properties limit their application range. Recently, we report extraordinary plasticity in an inorganic semiconductor, ZnS in darkness. Room-temperature deformation tests of ZnS were performed under varying light conditions. ZnS crystals immediately fractured when they deformed under light. On the other hand, it was found that ZnS crystals can be plastically deformed up to a plastic strain of 45 % in darkness. In addition, the optical band-gap of the deformed ZnS was decreased by 0.6 eV. These results suggest that dislocations in ZnS become extremely mobile in darkness and that multiplied dislocations can affect the optical band-gap over the whole crystal.</p>

DOI： 10.11470/oubutsu.90.3_176

CiNii Research

Language：Japanese   Publisher：The Japan Institute of Metals and Materials  

DOI： 10.2320/materia.60.30

CiNii Research