The interaction of neutral vacancies and interstitials with the clean $\text{Si}\left(001\right)$ surface is studied using density functional theory calculations within the generalized gradient approximation. We find both vacancies and interstitials within topmost three subsurface layers are significantly stabilized by their strong interactions with the surface. Their formation energies are predicted to be a few eV lower than those at the bulk. This study suggests that a large fraction of neutral interstitials may reside in the subsurface layers. However, most vacancies will eventually remain in the form of missing dimers due to their significant formation energy difference. Along with structure and energetics, we analyze bonding of vacancies and interstitials based on electron density and electron localization function topologies. We also show the diffusion pathways and barriers of vacancies on the surface and at the subsurface layers.

• Received 27 August 2003

DOI:https://doi.org/10.1103/PhysRevB.70.045321