Effect of sputtering power on the structural and optical properties of CdS films

CdS thin films were prepared by radio frequency magnetron sputtering with different sputtering power. The effects of sputtering power on crystallinity, surface morphology and optical properties of the films were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-visible transmission spectra. The XRD measurement revealed that CdS films were polycrystalline and retained the mixed structure of hexagonal wurtzite and cubic phase. As the power increased, the H(002)/C(111) peak was more intense and sharper. This indicates that the CdS films are grown with the preferred orientation of the H(002)/C(111) plane at higher power, resulting in improvement in the film crystallinity. The morphology of all films was found to be continuous and dense. An increase in the power from 60 to 120 W, the optical band gap decreased from 3.44 to 2.42 eV.