Oxygen deficiency and V and Sb doping in TiO2 and SnO2: Influences on surface electronic structure

Book section

The influence of oxygen deficiency and of doping with V and Sb on the surface electronic structure of TiO2 and SnO2 will be reviewed. Despite the similarity in structure of the two materials, they differ significantly in their surface electronic properties. Oxygen deficiency in TiO2-x gives rise to a new electronic state in the top half of the bulk bandgap due to electrons self trapped on Ti(III) sites, whereas in SnO2-x new 5s-5p hybrid states appear toward the bottom of the bulk bandgap. V-doping in both TiO2 and SnO2 gives rise to localized V(IV) states, whose adiabatic ionization energy defines the Fermi energy. A shift of 0.6 eV between the vertical ionization energies in the two systems is shown to be due to the differing vibrational relaxation energies associated with very different high frequency dielectric constants for the two oxides. Finally the effects of Sb doping are considered. Sb doped SnO2 is a metallic conductor with electrons in the Sn 5s conduction band. By contrast, Sb doping in TiO2 is compensated by cation vacancies and the material is a white insulator. However for both compounds, surface Sb(III) give rise to localized 5s-5p hybrid states.

Authors: Egdell, R

• Publisher: Trans Tech Publ
• Volume: 111-112
• Pages: 11-38
• Publication date: 1995-01-01