Molecular dynamics simulation of the early stages of self-interstitial clustering in silicon

We have studied the early stages of self-interstitial clustering in silicon using molecular dynamics simulation techniques. We have generated silicon samples of over 200,000 atoms where we introduced a 0.5% extra concentration of self-interstitials. Then samples were annealed at several temperatures. During the simulations we observed the formation of interstitial clusters with different atomic structures, ranging from spherical and amorphous-like clusters, to highly ordered extended configurations such as (110) chains, {111} rod-like defects and dislocation loops, and {100} planar defects. This last type of defects, while common in germanium, have not been observed in silicon until very recently, in ultra-fast laser annealing experiments. The particular morphology of formed interstitial clusters is found to be related to the annealing temperature, as it is observed in the experiments. From the molecular dynamics simulations we have analyzed the atomic mechanisms leading to the formation and growth of interstitial clusters, with special attention to the newly found {100} planar defects.