Integrated atomistic modelling of interstitial defect growth in silicon

A new theoretical approach that combines Metropolis Monte Carlo, tight-binding molecular dynamics, and density functional theory calculations is introduced as an efficient technique to determine the structure and stability of native defects in crystalline silicon. Based on this combined approach, the growth behaviour of self-interstitial defects in crystalline Si is presented. New stable structures for small interstitial clusters (In, 5n16) are determined and show that the compact geometry appears favoured when the cluster size is smaller than 10 atoms (n10). The fourfold-coordinated dodeca-interstitial (I12) structure with C2h symmetry is identified as an effective nucleation centre for larger extended defects. This work provides the first theoretical support for earlier experiments that suggest a shape transition from compact to elongated structures around n=10. We also provide some theoretical evidence that suggests that {311} extended defects grow slowly along 233 and relatively faster along 110, which is consistent with typical defect aspect ratios observed through transmission electron microscopy.