Toward a New Understanding of Dislocation Behavior in Inorganic Semiconductor Materials and Further Development of Novel Functionalities from Dislocations

Abstract

It is well known that light environment affects the mechanical properties of inorganic semiconductor materials, but still little is understood about the detailed mechanism. We before reported that single-crystalline zinc sulfide, an inorganic semiconductor material, exhibits significant plasticity in the dark. This finding has prompted us to investigate the effect of light environment on the dislocation behavior of inorganic semiconductor materials once again. On the other hand, in understanding the effects of light environment on dislocation behavior, it is difficult to obtain large, millimeter-sized crystals of advanced inorganic semiconductor materials to which conventional mechanical tests can be applied. Therefore, one of the main goals of our research project is to establish a method to understand dislocation behavior at the nanoscale by constructing a new nanoscale mechanical testing system that can be applied to thin substrates under controlled light environment. We have successfully constructed a new nanoindentation system (we call Photoindentation) in which light can be quantitatively applied below the indenter from two directions at the same time, and conducted creep tests in which a constant load is applied at or above the load at which dislocations occur (pop-in stress). In addition, care was taken to obtain statistically correct experimental results by conducting a great number of experiments. As a result, it was demonstrated that light has little effect on the nucleation of dislocations, while light has a strong effect on the glide motion of dislocations. In addition to these nanoscale experiments, macroscale experiments have been conducted in an effort to further understanding of light environment effects on dislocation behavior.