[P2-79] Atomistic insights into defect formation mechanism in single crystal SiC based on molecular dynamics simulation
Silicon carbide (SiC) is a promising next-generation semiconductor for high-power, high-temperature, and high-voltage devices because of its wide bandgap, high breakdown field, and high thermal conductivity. However, the efficient and smooth machining of SiC is technically difficult due to its intrinsic nature of high hardness and brittleness as well as strong anisotropy. It is still a great challenge to understand machining processes in which damage layers caused by stress-induced phenomena such as plastic deformation and fracture are introduced beneath grinding surface. In this study, we perform one million-atom molecular dynamics simulations of nanoindentation tests on cubic SiC single crystal using a nano-sized spherical indenter to clarify the plastic deformation mechanism and defect formation criteria in SiC. An analytical bond-order Tersoff-type interatomic potential for SiC developed by Erhart et al., which reproduces the elastic, defect, and thermal properties, is adopted. The load-displacement curves of the nanoindentation tests obtained by our simulations demonstrate transition from elastic deformation to plastic deformation so-called “pop-in” event. Our results also predict the decrease of the CRSS (critical resolved shear stress) of single crystal SiC with increasing temperature from 300 K to 2000 K for both (001) and (111) indent, which means less energy is required to activate slip systems at higher temperature. These results are similar to the feature of ductile materials such as metals, although SiC is known as brittle materials. In addition, we identify crystalline slips and defects generated beneath the indenter after the pop-in event by means of a novel type of structural analysis method using sub-lattice of Si or C which is based on common neighbor analysis. The structural analysis we propose reveals that dislocation loops in {111} planes which correspond to the slip plane of SiC are developed with increasing indenter depth. Furthermore, we find that for lower temperature perfect dislocations are dominantly formed, while for higher temperature partial dislocations together with stacking faults are superior to the perfect dislocations, resulting in the dramatic increase of the partial dislocations.