NATURE OF DONOR STATES IN V-DOPED SNO2

The influence of vanadium doping on the electronic structure of SnO2 has been studied by a range of techniques including X-ray and ultraviolet photoemission spectroscopy, as well as IR reflectance and magnetic susceptibility measurements. In contrast to Sb, V does not act as a shallow n-type dopant in SnO2 and V substitution appears to be largely compensated by cation vacancies or oxygen interstitials. However, a state is apparent in ultraviolet photoemission toward the bottom of the bulk bandgap of SnO2. This corresponds to electrons trapped on V-IV ions close to the surface of the doped material. The binding energy of the V-IV state in doped SnO2 is compared with that in V-doped TiO2 and the differences between the two materials are shown to be consistent with a simple dielectric model.