Chemical bath deposition and characterization of zinc sulphide thin film for possible device application
This work involved the chemical bath deposition (CBD), and study of the optical and solid state properties of zinc sulphide films for possible device application. The zinc sulphide film was prepared from different host solutions comprising zinc sulphate and zinc chloride as precursors used, in order to ascertain the precursor type that is better for the deposition of zinc sulphide films. Ammonia solution was used as a complexing agent along with hydrazine hydrate as complementary complexing agent which facilitated the deposition time. The zinc sulphide film was deposited as optical coating on glass slide and the spectral transmittance data of the zinc sulphide films from both host solutions were estimated from UV-VIS spectrophotometer at normal incidence of light in the wave length range of 200-1100nm. The analysis of the optical properties show that the transmittance spectral of zinc sulphide film deposited from zinc sulphate has a maximum value of 75% in the visible/NIR of the spectrum which is higher than that of the other host solution. The absorbance spectral and absorption coefficient decreases as the photon wavelength increases for the zinc sulphide film deposited from zinc sulphate solution, but for the film from zinc chloride, it is different. The optical energy bandgap shows a higher value of 3.99eV for the sample deposited from the zinc sulphate solution. The analysis of the optical and solid state properties of the samples reveals that the zinc sulphide film deposited using zinc sulphate solution gives better qualities needed for application in devices such as solar cells, diodes and similar applications.
Keywords: CBD, ZnS, NIR, UV-VIS, Solar cells, Thin film