The microscopic model of the Si (001) crystal surface was investigated by first principles calculations to clarify the behaviour of intrinsic point defects near crystal surfaces. A c(4 x 2) structure model was used to describe the crystal surface in contact with vacuum. The calculations showed lower formation energy near the surface and the existence of formation energy differences between the surface and the bulk for both types of intrinsic point defects. The tetrahedral (T)-site and the dumb-bell site, in which a Si atom was captured from the surface and forms a self-interstitial, were found as stable sites near the third atomic layer. The T-site had a barrier of 0.48eV, whereas the dumb-bell site had no barrier for the interstitial to penetrate into the crystal from the vacuum. Si atoms in a melt could migrate and reach at the third layer during crystal growth when bulk diffusion coefficient was used. Therefore, the melt/solid interface was always a source of intrinsic point defects.

Ab initio Analysis of a Vacancy and a Self-Interstitial near Single Crystal Silicon Surfaces: Implications for Intrinsic Point Defect Incorporation during Crystal Growth from a Melt. E.Kamiyama, K.Sueoka, J.Vanhellemont: Physica Status Solidi A, 2012, 209[10], 1880-3