Structural and Electrical Properties of Copper Sulfide (CuS) Thin Films doped with Mercury and Nickel impurities

Abstract

Chemical bath deposited copper sulfide (CuS) thin films were doped with varying concentrations of mercury (Hg) and nickel (Ni) impurities (0.01-0.03M) on glass substrates at room temperature of 27 oC. X-ray diffraction (XRD) and four-point probe techniques were used to analyze the structural and electrical properties as well as the thickness of the doped CuS thin films. The XRD results reveal that the films have mono-crystallite structure with broadening of the diffraction peak by both impurities. Values of the Bragg’s angle obtained were 2ϴ = 29.28o for the diffraction peak of Ni impurities and 2ϴ = 27.86o for the diffraction peak of Hg impurities as compared to un-doped CuS thin films whose diffraction peak occurred at 2ϴ = 23.71o. The electrical resistivity of the films dropped from about 2000 Ω-cm for the un-doped CuS thin film to zero value for 0.01M of Ni impurities and then reversed from negative value back to zero for Ni impurities of equal to or greater than 0.02M concentration. For Hg impurities, the electrical resistivity first rose to 6,600 Ω-cm for 0.01M impurity, then dropped symmetrically back to 2000 Ω-cm for 0.02M impurity and gradually decreased with higher concentrations of Hg impurities. Corresponding variations in electrical conductivity, dielectric constants and film thickness with impurity concentrations are also reported in this paper