Role of defects in determining the electrical properties of CdS thin films. I. Grain boundaries and surfaces

Abstract

The relationship between the electronic properties of mobility and resistivity, and electron scattering from film defects in slowly deposited cadmium sulphide polycrystalline thin films is investigated. The correlation of these properties is accomplished in a direction parallel to the substrate (``in-plane'') where the defects of interest are grain boundaries and surfaces. The Petritz (grain boundary) theory is incorporated with surface-scattering theory to formulate a simple model which predicts the effect of these defects on the electron mobility. Typical values for the grain-boundary potential and surface-scattering length are 0.07 eV and 1100 Å at a substrate temperature of 180°C for these glass-deposited films. The mobility is found to depend strongly on grain size, which was a function of substrate temperature. Hall data are presented as a function of evaporation rate, substrate temperature, film thickness, and film temperature. Finally, the grain-boundary potential is found to depend on the fabrication parameters, especially the deposition rate.