Molecular dynamics simulation of irradiation-induced amorphization of cubic silicon carbide

It has long been observed that a crystalline-to-amorphous (c-a) transition occurs in silicon carbide (SiC) irradiated at low temperature. However, the microscopic mechanisms leading to the transition are not well understood. We report in this paper a molecular dynamics (MD) simulation of low-energy (100 eV) recoil accumulation at cryogenic temperature (20 K), up to ≈1 dpa, in which the irradiated computational sample becomes amorphous and is subsequently annealed at high temperature (2320 K). The simulation suggests that, at least for low-mass impinging particles, provided that no direct impact amorphization (DIA) takes place, the driving force for the c-a transition in this material is the accumulation of Frenkel pairs up to a critical concentration (≈1.9×1022 cm−3). The role of antisites in the process is negligible. In fact, antisite formation during the annealing could be the bottleneck for complete recovery. A simple and intuitive analytical model based on the concepts of recombination barriers and interstitial migration is also proposed, to describe the temperature dependence of the critical dose for amorphization.