Influence of the thickness on physical properties of chemical bath deposited hexagonal ZnS thin films

Hexagonal ZnS thin films of thicknesses ranging between 454 to 750 nm are deposited on a glass substrate by chemical bath deposition at 80 degrees C. The ZnS thin films are characterized by X-ray diffraction (XRD) and optical absorption spectroscopy. The films are shown to be crystallized in the hexagonal phase and present a preferential orientation along the c-axis by XRD measurements. Only one peak, corresponding to the (008) phase (2 theta=29.5 degrees), appears on the diffractograms. The ZnS films show a high transmission. The optical constants such as refractive index n, extinction coefficient k, real epsilon(1), and imaginary epsilon(2) part of dielectric constant are calculated in the visible region. A reduction in refractive index (n) and the extinction coefficient (k) is observed as film thickness decreases. The electrical conductivity decreased from 1.62x10(-9) to 1.32x10(-10) (Omega.cm)(-1) when the films are annealed at 400 degrees C for 1 hour. The temperature-dependent current was measured in the range 27-400 degrees C and the activation energy values were obtained using the temperature-dependent current measurements.