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Extraordinary plasticity of an inorganic semiconductor in darkness

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Science  18 May 2018:
Vol. 360, Issue 6390, pp. 772-774
DOI: 10.1126/science.aar6035

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Plastic in the dark

Inorganic semiconductors, such as silicon and gallium arsenide, are brittle materials. This property means that large single crystals are cleaved into thin sheets. Oshima et al. show that zinc sulfide is, in contrast, a plastic material if deformed in total darkness. Plastic deformation is likely inhibited when light is present because photoexcited charge carriers become trapped at these sites and pin them through electrostatic effects.

Science, this issue p. 772

Abstract

Inorganic semiconductors generally tend to fail in a brittle manner. Here, we report that extraordinary “plasticity” can take place in an inorganic semiconductor if the deformation is carried out “in complete darkness.” Room-temperature deformation tests of zinc sulfide (ZnS) were performed under varying light conditions. ZnS crystals immediately fractured when they deformed under light irradiation. In contrast, it was found that ZnS crystals can be plastically deformed up to a deformation strain of εt = 45% in complete darkness. In addition, the optical bandgap of the deformed ZnS crystals was distinctly decreased after deformation. These results suggest that dislocations in ZnS become mobile in complete darkness and that multiplied dislocations can affect the optical bandgap over the whole crystal. Inorganic semiconductors are not necessarily intrinsically brittle.

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