Electronic structure of steps on silicon (111) surfaces from theoretical studies of finite clusters

Generalized valence-bond and configuration-interaction calculations were carried out for models of the steps on (111) surfaces. A characteristic of the step is a divalent Si atom adjacent to a trivalent surface Si atom. The result is three localized electronic states separated by less than 0.3 eV. These states have quite different electronic structure than the surface dangling bond, and they are expected to be reactive toward a large range of chemical species.