The electrical conductivity of stannous sulphide

Abstract

The conductivity of stannous sulphide has been measured between the ordinary temperature and 400° C, and follows the expression K T = A 1 e - E 1 / kT + A 2 e - E 2 / kT . The low-temperature conductivity has been studied with particular reference to the effect of chemical treatment calculated to change any deviations from ideal stoich iometric composition. Treatment with hydrogen at temperatures below those at which reduction to tin can occur brings about a considerable decrease in conductivity; exposure to oxygen or to hydrogen sulphide restores the conductivity. The low-temperature conductivity is attributable to a stoichiometric excess of non-metal in the lattice, the current being transported by a corresponding number of positive holes. From the rate of diminution or restoration of conductivity, the positive holes must be located in the surface layers of atoms of the crystallites. The changes in conductivity resulting from changes in the stoichiometric defect arise almost entirely through the change in the activation energy of the conduction process, E 1 . Although not considered in the present theory of semiconductors, both E 1 and the electronic mobility are functions of the concentration of conducting centres. The high-temperature conductivity is attributed to the intrinsic conduction of the lattice, and indicates the existence of a conduction band about 1·2 eV above the full band.