Electronic Structure of the CdTe(100)-(1×1) Surface

Abstract

Unreconstructed CdTe(100) surface prepared by ion bombardment and annealing is investigated by angle-resolved photoemission. The experimental band structure E(k || ) is determined along high-symmetry lines of the surface Brillouin zone by measuring energy-distribution curves of photoelectrons. Different criteria were applied to separate surface and bulk related spectral features, e.g. calculating the position of bulk-derived emissions in the frame of the free-electron final state approximation assuming k conservation. In this way, most dispersing features could be explained. All remaining features were compared with theoretical surface band structures for different polar surface terminations which were calculated within a layer doubling procedure on the basis of an EHT-flt to the bulk band structure. The investigated CdTe(100)-(1x1) surface could be identified as Cd terminated. Two surface bands were observed, one located above the valence-band edge and the second in the open pocket of the projected bulk band structure along the Γ K direction. At 4.6 eV binding energy an additional weakly dispersing band was found, which contains mixed surface and bulk character. The high density of bulk states associated with this edge of the heteropolar gap is also expected to contribute to this feature.