A simple approach to covalent surfaces

Abstract
A 1-dimensional covalent surface is first studied selfconsistently within the narrow gap approximation. Our analysis shows : i) that the potential and charge distribution in the surface region behave rather like those for the case of a metal, and ii) that the dangling-bond surface state is determined by a charge neutrality sum-rule. A covalent 111-surface is then discussed. Our arguments strongly suggest that the same conclusions apply to this surface. By using these results, the 111-Si surface potential has been obtained and compared satisfactorily with other independent theoretical calculations