Investigation of growth phases of chemical bath deposited CdS thin films

Polycrystalline CdS thin films, ranging in thickness from 30 to 200 nm, have been chemically deposited onto glass substrates using an ammonia-cadmium-thiourea reaction solution. Using proton-induced X-ray emission and atomic force microscopy, these film´s elemental composition, thickness and microstructure have been examined. Analysis indicates that there is a distinct change from the continuous phase deposition to a particulate phase deposition and that these two different phases produce layers of CdS with different densities. Because of this change in density the point where the particulate CdS phase becomes the dominant deposition process can be identified. A mechanism is proposed to explain this difference in film densities.