Pop-in effects and dislocation nucleation of c-plane single-crystal ZnO by Berkovich nanoindentation

Abstract

In the present study, the Berkovich nanoindentation-induced multiple pop-ins phenomena are observed in the load–displacement curves of c-plane single-crystal ZnO. The results indicated that no evidence of phase transformation is revealed by using the cross-sectional transmission electron microscopy (XTEM) and the selected area diffraction (SAD) analyses. Instead the XTEM observations suggest that these “instabilities” might be resulted from the sudden nucleation of dislocations propagating along the slip systems lying on the {0001} basal planes and the {101¯1} pyramidal planes. Therefore, based on this scenario, an energetic estimation of dislocation nucleation is made. Further, the cathodoluminescence (CL) spectroscopy was examined as a function of applied indentation loading for the c-plane single-crystal ZnO. The results showed the near band-edge luminescence intensity falling exponentially with the applied nanoindentation load and reduced to about 5% of that obtained in pristine area as the maximum indentation load up to 100mN. It suggests that the CL technique may serve as an effective alternative for studying the near-surface plasticity semiconductors.