CdS Thin Films Deposited by CBD Method on Glass

Abstract

CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron microscope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X-ray diffraction results showed the film structure was a mixture of two phases: hexagonal and cubic, and it was very important to controll deposition time to the film's crystal phase. All films in depth of approximate 100 nm existed above 65% transmittance, the absorption edge became “red-shift" with temperature rising. At 60 and 70 °C, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90 °C, the energy band gap was less than 2.42 eV and increased little when the time changed from 10 min to 15 min at 80 °C.