Influence of substrate temperature on the structural, optical and electrical properties of CdS thin films deposited by thermal evaporation

CdS thin films were deposited onto glass substrates at three different temperatures (20, 100 and 200 °C) by vacuum thermal evaporation at 10−5 Torr using pure crystal as evaporated targets. The effects of substrate temperature on structural, electrical and optical properties were studied. Structural analysis using X-ray diffraction (XRD) and scanning electronic microscope (SEM) revealed that the films are polycrystalline in nature with a hexagonal wurtzite structure having (0 0 2) plane as the preferred orientation. The crystalline size (D), dislocation density (δ), strain (ε) and texture coefficient TC(hkl) were calculated. All the films have high optical transmittance (>80%) in the visible range. The optical band gap values are found to be in the range of (2.3–2.43 eV) and found to decrease with increase in substrate temperature. DC electrical conductivity was carried out at room temperature indicating a very low electrical conductivity.