Characterization of electrodeposited ZnTe thin films

Abstract

ZnTe thin films were deposited on FTO-coated glass substrates by a low-cost, easy and simple electrodeposition method. The grown layers of ZnTe have been characterized by photoelectrochemical cell (PEC) measurement for determining carrier type, UV–visible spectrophotometer for optical characterization, X-ray diffraction (XRD) for structural analysis and scanning electron microscopy (SEM) for the surface morphology. An annealing effect of the as-deposited thin films has also been investigated. PEC measurements of ZnTe film showed p type electrical conductivity. Optical measurement showed that ZnTe films have very high transmittance in the UV–visible region; moderate transmittance in the visible range; and moderate to lower transmittance in the visible–infrared region and have higher absorbance in the middle of the visible region to near-infrared region. Band gap values are estimated to vary from 2.3 to 1.90 eV for the ZnTe films deposited at different conditions. Band gap of ZnTe films is observed to decrease when the films are annealed at different temperatures in nitrogen environment. From the XRD and SEM study, ZnTe films are found to be polycrystalline with (111) preferential orientation of the cubic structure and appeared dense crack-free surfaces with regular granular-shaped grains without any cauliflower-like appearance. After annealing the as-deposited film transmittance, absorbance and intensity in XRD pattern are observed to increase and a good ZnTe crystal structure is observed to form. The values of average crystallite size are estimated to be 22.82 nm and 30.82 nm for as-deposited and annealed ZnTe films, respectively.