Molecular dynamics simulations of nanoindentation of -SiC with diamond indenter

We present the results of molecular dynamics simulations of nanoindentation of the Si-terminated (0 0 1) surface of cubic silicon carbide ( β -SiC) by a diamond tip. In particular, we investigate the dependence of the critical depth and pressure for the elastic-to-plastic transition as a function of indentation velocity, tip size, and workpiece temperature. The nature of the deformation at higher indentation depths is also considered. Our simulations were carried out using the Tersoff SiC potential, which accurately reproduces the lattice and elastic constants of β -SiC. Over the range of indenter sizes used in our simulations, both the critical pressure and the indentation depth decrease with increasing indenter size. Accordingly, the measured hardness is significantly higher than obtained experimentally for larger indenter sizes but decreases with increasing indenter size. In contrast, the critical indentation depth for the elastic-to-plastic transition does not depend on the indenter velocity over the range studied. For indentation depths beyond the critical depth, the pressure increases and saturates at 100 GPa, which corresponds to the experimental pressure at which β -SiC transforms to rocksalt structure. Thus, we conjecture that the observed plastic behavior is related to the onset of a phase transition from the cubic zinc-blende structure to the rocksalt structure under the indenter tip. This is in reasonable agreement with experimental studies of pressure-induced structural transformation in bulk SiC.