Argon implantation effects on the structural and the optical properties of vacuum evaporated CdS thin films

Vacuum evaporated cadmium sulphide (CdS) thin films were implanted with Ar⁺ at different doses. The X-ray diffraction (XRD) pattern of the as-deposited film showed a hexagonal structure with a preferred orientation along the (002) plane. Formation of Cd metallic clusters was observed in ion-implanted films from the XRD patterns. The band gap of the Ar⁺-implanted films decreased from 2.385 eV for the as-deposited film to 2.28 eV for maximum implantation whereas the absorption coefficient increased with increasing implantation dose. Raman scattering due to the Al(LO) phonon was observed at 299 cm^-1 in the as-deposited CdS film and had a large FWHM. The Raman peak position did not change much with the implantation dose. The FWHM increased with implantation at low doses due to increased lattice damage and decreased at higher doses due to an implantation-: induced annealing effect. The area under the Raman peak was found to be constant at low doses and to increase at the higher dose, probably due to implantation-induced surface roughness.