A molecular dynamics study of nanoindentation of amorphous silicon carbide

Through molecular dynamics simulation of nanoindentation of amorphous a-SiC, we have found a correlation between its atomic structure and the load-displacement (P-h) curve. We show that a density profile of a-SiC exhibits oscillations normal to the surface, analogous to liquid metal surfaces. Short-range P-h response of a-SiC is similar to that of crystalline 3C-SiC, e.g., it shows a series of load drops associated with local rearrangements of atoms. However, the load drops are less pronounced than in 3C-SiC due to lower critical stress required for rearrangement of local clusters of atoms. The nanoindentation damage is less localized than in 3C-SiC. The maximum pressure under the indenter is 60% lower than in 3C-SiC with the same system geometry. The onset of plastic deformation occurs at the depth of 0.5Å, which is ∼25% of the corresponding value in 3C-SiC. a-SiC exhibits lower damping as compared to 3C-SiC, which is reflected in the longer relaxation time of transient forces after each discrete indentation step.