Effect of chemisorbed oxygen on the electrical conductivity of Zn-doped polycrystalline SnO 2

Abstract

The electrical properties of sintered, zinc-doped SnO 2 have been shown to have a sensitive dependence on past history of treatment, even under conditions where bulk property changes are not to be expected. This has been related to its behavior as a semiconductor with a high degree of bulk compensation and the resultant importance of the additional compensation that can be provided by changes in the surface density of chemisorbed oxygen. Support for the chemisorption mechanism is afforded by dark current changes following different temperature—ambient gas pressure treatments and by observations of the current decays following rapid oxygen uptake in the dark or cessation of bandgap wavelength illumination. For the latter two cases the current and the inverse of the current, respectively, have a logarithmic dependence on time. This is shown to be consistent with an increase in chemisorption density which obeys Elovich kinetics.