Diffusion of small self-interstitial clusters in silicon: Temperature-accelerated tight-binding molecular dynamics simulations

Temperature-accelerated tight-binding molecular dynamics simulations show that self-interstitial clusters formed from two and three defects are mobile species. In particular, the di-interstitial (I₂) cluster is found to diffuse nearly as fast as the single self-interstitial (dumbbell) over a wide temperature range. In particular, at room temperature I₂ is found to diffuse at a rate similar to the dumbbell, thus making an important contribution to silicon self-diffusion at temperatures relevant for silicon bulk processing. The simulations also reveal the atomistic mechanisms responsible for the defects' mobility, showing that the I₂ cluster must be promoted to a metastable state in which it executes several diffusive events before decaying to a new ground-state configuration equivalent to the initial one.