Electronic structure of point defects on oxide surfaces

Abstract

We report results of a theoretical study of the electronic structure of point defects on semiconducting oxide surfaces, with an application to ${\mathrm{SnO}}_2$(110). The scattering theoretical method is used and detailed formal developments are given for the rutile crystal structure. For the ${\mathrm{SnO}}_2$(110) surface a series of monovacancy and divacancy models are studied, corresponding to the removal of one or two atoms from the outer surface layers. None of these defect models gives rise to a bound defect state in the optical gap. Similar to the case of the defect-free surface, the main defect-induced features are O p–derived resonances in the valence-band region and Sn s–derived resonances in the conduction-band region. The results are interpreted in terms of the ionicity of the material and compared with those for other oxide surfaces.