Atomic densities of states near Si (111) surfaces

Abstract

The semiempirical tight-binding method is used to construct accurate valence bands for bulk Si and Ge using Hamiltonian parameters through second neighbors. One additional parameter is used to describe surface relaxation (back-bond contraction). The density of surface bands and resonances associated with atomic layers near the surface is calculated. Surprisingly, the resonances are found to contribute to the surface density of states almost as effectively as proper surface states. Comparison with ion-neutralization, electron-energy loss, and ultraviolet photoemission data is made.