| Abstract Scope |
Wide-bandgap semiconductor crystals often fracture before appreciable plastic deformation at room temperature, but previous studies of photoplastic phenomena in ZnS showed that illumination can modify deformation behavior. This presentation focuses on photoindentation, that is, nanoindentation under controlled illumination, to examine light-sensitive plasticity in small stressed volumes. In ZnO and GaN, measurements on different crystal surfaces are used to compare the first pop-in event with indentation creep, hardness, and subsequent pop-in events. The first pop-in stress is not markedly changed by illumination, whereas indentation creep and subsequent plastic deformation are suppressed. These results indicate that the light effect appears mainly after dislocation nucleation, through changes in dislocation motion. The orientation dependence of the response is discussed in terms of activated slip systems and indentation-induced dislocation structures. |