Effects of mercury and nickel impurities on optical properties of copper sulfide (CuS) thin films deposited by chemical bath technique.

Abstract

Thin films of copper sulfide (CuS) with varying concentrations of mercury (Hg) and nickel (Ni) impurities (0.01M-0.03M) were grown on glass substrates at room temperature (300K) using chemical bath deposition technique. Spectral transmittance and reflectance of the thin films were measured with a spectrophotometer in the UV-Vis-IR region of the electromagnetic spectrum. The effects of the impurities on other optical spectra obtained theoretically were quantitatively evaluated from the spectrophotometer data . The energy band gap increased for all Hg impurity concentrations to a maximum of 3.25 eV for 0.02M Hg impurity as against 2.65 eV for as grown CuS thin film, while the band gap decreased for all Ni impurity concentrations to a minimum of 1.85 eV for O.01M Ni impurity. The absorbance increased with both Hg and Ni impurity concentrations while the transmittance decreased with Ni impurities and increased with Hg impurities. The results also show increase in absorption coefficient and decrease in reflectance for both Hg and Ni impurities with a maximum reflectance of 70% for as grown thin film down to 10% wlth 0.01 Ni impurity. Values for the refractive index reduced to 1.0 with 0.01M of both impurities from a maximum of 2.4 for as grown CuS thin film. Also, results of the absorbance, transmittance and reflectance as presented here converged at 300 nm and diverged to 900 nm wavelength limit.