Energetics and approximate quasiparticle electronic structure of low-index surfaces of SnO ₂

The geometry and energetics of the unreconstructed tin- and oxygen-terminated (100), (010), and (110) surfaces, the tin-terminated (111) surface, and the stoichiometric (001) surface of rutile-SnO ₂ are investigated. Total energies and relaxed atomic geometries are calculated within density functional theory using the local density approximation (LDA). We conclude from these results that the (110) and (100) surfaces are most stable. Their termination depends on the experimental situation: While under oxygen-rich preparation conditions the oxygen termination is preferred, reduced surfaces are more likely to occur in the oxygen-poor limit. In addition, electronic band structures and densities of states are calculated using a recently developed approximate quasiparticle approach, the LDA-12 method. Except for the SnO-terminated (110) surface, all other faces are found to be insulating and O- or Sn-derived surface states appear in the projected bulk fundamental gap. While the surface barrier heights vary by more than 2eV with orientation and termination, the ionization energies tend to the smallest values for the energetically favored surfaces.