Atomic-scale simulation of displacement cascades and amorphization in beta-SiC

Molecular dynamics (MD) methods with a modified Tersoff potential have been used to simulate Si displacement cascades with energies up to 50 keV and t o compare clustering behavior for Si and Au recoils in beta -SiC (3C). The results show that the lifetime of the thermal spike is very short compared to that in metals, and that the surviving defects are dominated by C inters titials and vacancies for Si displacement cascades. Only 19% of the interst itial population is contained in clusters, with the largest cluster contain ing only four interstitial atoms for energetic Si recoils. The energy depen dence of stable defect formation exhibits a power-law relationship. The hig h energy Si recoil generates multiple sub-cascades and forms dispersed defe ct configurations. These results suggest that in-cascade amorphization in S iC doss not occur with any high degree of probability during the lifetime o f Si cascades. On the other hand, large disordered domains are created in t he cascades produced by 10 keV Au recoils. Structure analysis indicates tha t these highly disordered regions have amorphous characteristics. The data for the cluster spectra have been used to calculate the relative cross-sect ions for in-cascade amorphization (or clustering) and defect-stimulated amo rphization. The ratios of these cross-sections for Si and Au are in excelle nt agreement with those derived from a fit of the direct-impact/defect-stim ulated model to experimental data. (C) 2001 Elsevier Science B.V. All right s reserved.