Influence of growth process on the structural, optical and electrical properties of CBD-CdS films

The hexagonal cadmium sulphide (CdS) thin films with strong (002) orientation are successfully prepared by chemical bath deposition (CBD) technique using the reaction between CdCl2 and CS(NH2)2. Especially, polyglycol is used to modify the CBD system without magnetic agitation. The influence of bath temperature on the properties of the CdS films such as optical transmission, surface morphology and the structure is researched. The results show that polyglycol can flatten the films and diminish the pinhole. X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests verify that the deposited CdS films presented a hexagonal structure and no secondary or mixed phases are found. A preferential columnar growth parallel to the substrate edge is also observed. It is found that the bath temperature plays a vital role on the quality of the CdS films. The increase of bath temperature improves the surface morphology of the CdS films and also diminishes pinholes on the films. The optimum bath temperature is 85 °C. The band gap calculated from transmission spectra is about 2.56-2.336 eV.