Molecular dynamics methods, using a modified Tersoff potential, were used to simulate Si displacement cascades with energies of up to 50keV and to compare the clustering behaviors of Si and Au recoils in β-phase material. The results showed that the lifetime of the thermal spike was very short, when compared to that in metals, and that the surviving defects were dominated by C interstitials and vacancies for Si displacement cascades. Only 19% of the interstitial population was contained in clusters; with the largest cluster containing only 4 interstitial atoms for energetic Si recoils. The energy dependence of stable defect formation exhibited a power-law relationship. High-energy Si recoils generated multiple sub-cascades and formed dispersed defect configurations. The results suggested that in-cascade amorphization did not occur, with any high degree of probability, during the lifetime of Si cascades. Large disordered domains were created in the cascades produced by 10keV Au recoils. Structural analysis indicated that these highly disordered regions had amorphous characteristics. Data for the cluster spectra were used to calculate the relative cross-sections for in-cascade amorphization (or clustering) and defect-stimulated amorphization. The ratios of these cross-sections, for Si and Au, were in very good agreement with those deduced by fitting the direct-impact/defect-stimulated model to experimental data.

Atomic-Scale Simulation of Displacement Cascades and Amorphization in β-SiC. F.Gao, W.J.Weber, R.Devanathan: Nuclear Instruments and Methods in Physics Research B, 2001, 180[1-4], 176-86