Deviations from Arrhenius behavior in the dark conductance of Inhyphen;doped CdS films

摘要

The dark electrical conductivity sgr; of Inhyphen;doped CdS films does not show a simply activated behavior. Appreciable curvature is seen in graphs of logthinsp;sgr; vsTminus;1. This has been attributed to a temperaturehyphen;dependent activation energy or to a tendency of sgr; towards saturation at low temperatures. We suggest that it arises because, as the doping is reduced, the data tend to follow logthinsp;sgr;=constTrather than logthinsp;sgr;=constthinsp;Tminus;1. This linear temperature dependence of logthinsp;sgr; has also been seen for offhyphen;stoichiometric SiO2films, among other lowhyphen;conductivity solids, and we point out that it is a characteristic behavior which was anticipated more than 20 years ago in a model of quantum tunneling through a vibrating barrier.