Effect of Sputtering Power on the Properties of RF-Sputtered SnS Thin Films

SnS thin films were grown on soda-lime glass substrates by RF magnetron sputtering. The sputtering power was varied from 80 to 140 W in 20 W increments. The effects of the sputtering power on the structural and optical properties of SnS thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy (Raman), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and ultraviolet-visible-near infrared spectrophotometry (UV-Vis-NIR). The results revealed that the films were polycrystalline and the XRD patterns matched well with the orthorhombic structure and the preferred orientation along the (111) plane. As the sputtering power increased, the films exhibited an increasingly oriented structure with better crystallinity. The highest intensity peak of the Raman measurement was at 222 cm^–1, which belongs to the symmetrical stretching of the Sn-S bond and showed a small shift as the sputtering power varied. The surface morphology indicated that the films deposited at high power had enhanced particle size and nucleation over the films prepared with low growth power. The direct band gap decreased from 1.77 to 1.36 eV as the sputtering power increased from 80 to 140 W.