The homopolar amorphous surface Structural and electronic properties

Abstract

Abstract For the first time, the topological dependency of the density of states for the amorphous surface is calculated. The unrelaxed amorphous surface for homopolar semiconductors is briefly defined and described. A model Hamiltonian for computing the configuration-averaged density of surface states is used. A surface from a model with only even-fold rings and a surface from a model with both even-fold and odd-fold rings are investigated. The results are interpreted in terms of the effects of nearest-neighbour surface atoms, the number of unsaturated bonds/surface-atom and the ring structure. The odd-fold rings cause the distribution of the surface density of states to be spread over a larger energy region than for models where the odd-fold rings are absent. It is argued that the amorphous topology must be taken into account when considering models for the gap states. For a tetrahedral solid, the surface states are expected to contribute to the filling of the minima in the bulk valence-band density of states.