Influence of oxygen on structural and optoelectronic properties of CdS thin film deposited by magnetron sputtering technique

In this study, CdS thin films with thicknesses of approximately 100 nm were deposited at a substrate temperature of 100 degrees C by a sputtering technique under two different ambient conditions-pure Ar ambient and Ar/O-2 (99:1) ambient-at deposition power densities of 1.0 and 2.0 W/cm(2), respectively The films were polycrystalline with a preferential orientation along the (002) crystal plane; however, the films deposited in the Ar/O-2 ambient exhibited reduced crystallinity. Furthermore, the crystallite sizes, micro-strains, and dislocation densities of the films were significantly affected by oxygen diffusion into the films' crystal structures. The CdS films deposited in the Ar/O-2 ambient demonstrated higher optical transmittance and higher bandgaps. Morphologies observed from scanning electron microscopy images revealed that the grains of the films were also significantly affected by the oxygen present in the deposition ambient. Additionally, photoluminescence analysis revealed that the sulfur vacancies in the CdS films were partially filled by oxygen atoms, causing significant variations in the electrical properties of the films.