The stability and migration of self-interstitials were studied by performing first-principles self-consistent pseudopotential calculations. It was predicted that the neutral Si interstitial would be lowest in energy at a [110]-split site, with energy barriers of 0.15 to 0.18eV for migration into hexagonal and tetrahedral interstitial sites. The migration barrier between an hexagonal site and a tetrahedral site was lower (0.12eV). These migration barriers were further lowered by successive changes in the charge state at various sites. This permitted the athermal diffusion of interstitials at very low temperatures. The [110]-split geometry was also the most stable structure for negatively charged states, while positively charged self-interstitials had the lowest energy at tetrahedral sites. In addition to the migration barrier, the formation energy of the [110]-split interstitial was estimated to be equal to about 4.19eV. The resultant activation enthalpy of about 4.25eV was therefore in good agreement with high-temperature experimental data.

First-Principles Study of the Self-Interstitial Diffusion Mechanism in Silicon. W.C.Lee, S.G.Lee, K.J.Chang: Journal of Physics - Condensed Matter, 1998, 10[5], 995-1002