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 VIV ions close to the surface of the doped material. The binding energy of the VIV 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