DEPENDENCE OF RESISTIVITY AND PHOTOCONDUCTIVITY IN EVAPORATED CADMIUM-SULFIDE THIN-FILMS ON DEPOSITION AND ANNEALING CONDITIONS

The resistivity of evaporated thin films of CdS has been measured as a function of deposition and annealing conditions. Resistivity was found to be thermally activated with a high temperature activation energy of approximately 0.5 eV, which was identified with the height of the inter-crystalline barrier in the Petritz model. Resistivity decreased with increasing film thickness and annealing temperature and increased with increasing deposition rate and substrate temperature during deposition. It is proposed that these variations are related to previously reported changes in the microcrystallite grain size and the degree of preferential orientation in the [002] direction. In addition resistivity is also dependent on compositional changes during the deposition process and mobility variations due to surface scattering. Preliminary results indicate that the films are weakly photoconductive, with lower photosensitivity for the thicker films.