Effect of ammonium sulphate on chemical bath deposition of CdS thin films

CdS semiconductor thin films have been deposited by chemical bath technique from an aqueous solution consisting of cadmium sulphate and thiourea. The deposition of CdS thin films depends on various parameters like pH, temperature, concentration of complexing agents and concentration of reactants (cadmium sulphate and thiourea). The ammonia evaporation from bath affects the pH of the solution and hence the amorphous film is obtained. In order to overcome this problem, a chemical bath deposition system has been modified to obtain precise control over the pH of the solution by adding ammonium sulphate as a complexing agent along with ammonia. The addition of the second complexing agent improved the quality of CdS thin films deposited on a glass substrate. XRD studies show that as deposited films have a cubic structure and annealed films have a hexagonal structure. The surface morphology of the film has been analysed by means of the scanning electron microscope.