Light irradiation induced brittle-to-ductile and ductile-to-brittle transition in inorganic semiconductors

The intrinsic brittleness of inorganic semiconductors prevents them from extended engineering applications under extreme conditions of high temperature and pressure, making it essential to improve their ductility. Here, we applied the constrained density functional theory to examine the relationship between plastic deformation and photonic excitation in sphalerite ZnS and related II-IV semiconductors. We find that ZnS transforms from a dislocation dominated deformation mode in the ground state to a twin dominated deformation mode with bandgap electronic excitations, leading to brittle failure under light illumination. This agrees very well with recent mechanical experiments on single crystal ZnS. More interesting, we predict that the ZnTe and CdTe display the opposite mechanical behavior compared to ZnS, exhibiting ductility close to metallic level with bandgap illumination, but typical brittle failure in the dark state. Our results provide a general approach to design more shapeable and tougher semiconductor devices by controlling exposure to electronic excitation.