The effect of Cu-doping on CdS thin films deposited by the spray pyrolysis technique

Abstract

Pure CdS and Cu-doped CdS thin films were deposited using the spray pyrolysis technique and characterized using XRD, XPS, AFM, UV-VIS spectroscopy and two probe DC-conductivity measurements. 2%, 4% and 6% Cu-content was used for doping. The particle size was found to decrease from 28nm to 25.4nm upon Cu-doping. The influence of Cu-doping on the stress and dislocation per unit volume has been estimated from the XRD data. AFM images of the annealed films show changes in morphology with increase in surface roughness from 25nm to 31nm with Cu-6% doping. Reflectance and transmission measurements were studied in the spectral range of 200–1100nm to extract the optical properties variation upon copper doping. Also the band gap was found to decrease from 2.43 to 2.39eV with increase in copper content. The electrical conductivity was measured by direct record of the resistance against temperature. All films show a semiconducting behavior and incorporation of Cu on CdS increases its activation energy.