Atomic-level computer simulation of SiC: defect accumulation, mechanical properties and defect recovery

Abstract

Damage accumulation simulated previously (F. Gao and W.J. Weber, Phys. Rev. B 66 024106 (2002)) has been used to study volume swelling of 3C–SiC, and to calculate the elastic constants, bulk and elastic moduli of the cascade-amorphized SiC. The swelling increases rapidly with dose at low-dose levels, but the rate of increase decreases dramatically at higher dose with a saturation volume change of 8.2% for the cascade-amorphized state. The elastic constants in the cascade-amorphized SiC decrease by about 19, 29 and 46% for C₁₁, C₁₂ and C₄₄, respectively, and 23% for bulk and elastic moduli. In order to understand defect annealing of damage accumulation, the stable Frenkel pairs created at low-energy events have been annealed at different temperatures, using molecular dynamics methods, to determine the time required for interstitials to recombine with vacancies. The results show that the low activation energies qualitatively overlap with experimental values determined for defect recovery below 300 K. Thus, the present results suggest that this experimental recovery stage is associated with the spontaneous recovery of Frenkel pairs.

Acknowledgements

This research was supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DE-AC06-76RLO 1830.