Effect of sputtering pressures and substrates on the properties of CdS films by annealing of precursors

In this paper, cadmium sulfide (CdS) films were prepared by annealing the precursors which were obtained with different sputtering pressures and substrates (quartz glass, Si wafer and glass) via sputtering-evaporation-sputtering (SES) method. The properties of the CdS films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscope, UV–Vis spectrophotometer and photoluminescence . Results indicated that the hexagonal CdS films were obtained at appropriate sputtering pressure (>1 Pa), and their grain size ranged from 14 nm to 44 nm. During the annealing, the conversion of the precursors to CdS films occurred, accompanied by the Cd volatilization. Additionally, the CdS films had good transmittance and the bandgaps of 2.32–2.36 eV. Besides, the rougher substrate surface led to the formation of the rougher film. The best quality CdS films were obtained at 2.8 Pa, using a quartz glass substrate. Its strong green emission peak originated from the transition from sulfur vacancies to sulfur interstitials. The weak red emission peaks of the other CdS films was attributed to sulfur vacancy defects . The vacancy-related emission behavior in annealed films was mainly affected by their composition. The results show that desirable CdS films prepared by annealing SES precursors can be suitable for different device applications. • Desirable CdS films were prepared by annealing precursors. • Precursors were prepared by sputtering-evaporation-sputtering method. • Sputtering pressure and substrate had great effects on the properties of CdS films. • This study provided a controllable and low-cost preparation process of CdS films.