Understanding the underlying mechanism of the first pop-in event under nanoindentation of 6H–SiC

This paper aims to investigate the underlying mechanism in the load-displacement curve corresponding to the first pop-in event during nanoindentation on 6H–SiC surfaces. It was found that the first pop-in event in the load-displacement curve was attributed to stress-induced amorphization. The resulting amorphous SiC phase exhibited volumetric expansion due to its reduced density compared to the crystalline phase. Despite identical testing conditions, the critical load for the first pop-ins showed significant variability across repeated experiments. This variability was quantitatively analyzed using cumulative probability distributions. The statistical behavior was further interpreted in terms of the attempt frequency and the applied shear stress required for the activation volume, highlighting the dominant role of amorphization in the deformation mechanism. These findings provide new insights into the stochastic nature of incipient plasticity in 6H–SiC.