Intrinsic and defect surface states on single‐crystal metal oxides

Abstract

The electronic properties of the surfaces of several single‐crystal metal oxides have been studied by electron spectroscopic techniques, yielding information on both intrinsic and extrinsic (defect) surface states. SrTiO3 and TiO2 have no intrinsic band‐gap surface states, while nearly perfect MgO(100) surfaces exhibit a cation‐derived empty surface state about 2 eV below the bulk conduction band edge. Defect surface states generally involve 0 vacancies, with attendant charge transfer to surface cations that results in occupied states in the band‐gap region.