Influence of bismuth doping on the structural and optical properties of ZnS thin films and nanopowders

Zn_(1−x/2)Bi_x/3S (x = 0, 0.03, 0.09) thin films and nanopowders synthesized by the simple chemical bath deposition technique were characterized using x-ray diffraction (XRD), scanning electron microscope, energy dispersive x-ray analysis, an atomic force microscope (AFM) and ultraviolet visible (UV–Vis) and photoluminescence spectroscopy. XRD analysis revealed a sphalerite structure for Zn_(1−x/2)Bi_x/3S (x = 0, 0.03, 0.09) thin films. However, the XRD pattern of Zn_(1−x/2)Bi_x/3S (x = 0.09) nanopowder revealed the co-existence of both sphalerite and hexagonal (wurtzite) phases. The crystallite size of Zn_(1−x/2)Bi_x/3S (x = 0, 0.03, 0.09) nanopowders were found to be in the range of 2–4 nm. AFM studies revealed that the film quality of Zn_(1−x/2)Bi_x/3S (x = 0.09) was relatively good compared to other films. A notable decrease in the band gap of both the thin films and nanopowders were observed with incorporation of Bi³⁺ in ZnS. These results indicate that Bi doped ZnS can be used to enhance the photocatalytic H₂-production activity under visible and UV light. (paper)