ABSTRACT

 Thin films of copper sulphide (CuS) with varying concentrations of mercury (Hg) and nickel (Ni) impurities (0.0 I M-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 3.25e V for 0.02M Hg impurity as against 2.65eV for as grown CuS thin film, while the band gap decreased for all Ni impurity concentrations to a minimum of 2.00eV for 0.0lM 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 69.8% for as grown thin film down to 13.2% with 0.01 Ni impurities. Values for the refractive index reduced to 1. 1 with 0.0 IM 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. The electrical properties were characterized; the films with Ni impurities exhibited high conductivity with a maximum value of 6666.67x10Q'cm' ', as the concentration of the Ni impurity increases, the conductivity increases. The films with Hg impurities exhibited high electrical resistivity with a maximum value of 6643.002cm; as the concentration of the Hg impurity increases, the conductivity decreases. The XRD result revealed that the thin films are monocrystalline in nature due to presence of a peak xiv respectively. The films could be very useful in different applications; their high absorbance makes them useful in window coating for people living in the hot climate like Nigeria. They could be useful in making glasses for protection from sun burns caused by UV radiations. The properties of poor transmittance in the UV-VIS but moderately high transmittance in the VIS-NIR exhibited make the film good material for screening of UV portion of electromagnetic spectrum which is dangerous to human health and as well hannful to domestic animals. The films can be used for coating eye glass for protection from sunburn caused by UV radiations. The index of refraction n >0 makes the thin films good candidates for protective coatings. The maximum values of optical conductivity of the deposited thin films are all of the order I 0 14 s· 1 and these high values imply high electrical conductivity. The results provide basis for specific applications in microelectronics for fabrication of computer memories, multipler condensers etc.