Influence of preparation technique on the structural, optical and electrical properties of polycrystalline CdS films

CdS films were prepared by three different techniques-vacuum evaporation (VE), screen printing (SP), and chemical bath deposition (CBD). The influence of the preparation technique on the structural, optical and electrical properties of the polycrystalline CdS films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical transmission and electrical resistivity. Evaporated and chemical bath deposited films were polycrystalline with a preferred (002) orientation. Film optical parameters (n, k, alpha, E-g) were evaluated and correlated with the preparation technique. The electrical resistivity of VE films is found to be about one hundredth of the resistivity of an SP film, and one millionth that of a CBD film. The effects of film thickness on the structural, optical and electrical properties of CdS film were also studied. It was found that the optical absorption edge shifted to a higher wavelength with increasing film thickness and electrical resistivity decreased with increasing film thickness; this was attributed to the effect of crystallite size, the degree of preferred orientation, internal microstrain and stoichiometry of the film. (C) 1998 Elsevier Science Ltd All rights reserved.