Argon and nitrogen implantation effects on the structural and optical properties of vacuum evaporated cadmium sulphide thin films

Abstract

We have implanted vacuum evaporated cadmium sulphide (CdS) thin films with Ar+ and N+ at different doses. We have analysed the properties of the ion-implanted CdS thin films using x-ray diffraction, optical transmittance spectra and Raman scattering, and we observed the formation of Cd metallic clusters in the ion-implanted films. The bandgap of the Ar+-doped films decreased from 2.385 eV for the undoped film to 2.28 for maximum doping. For the N+-doped film the bandgap decreased from 2.385 to 2.301 eV, whereas the absorption coefficient values increased with the increase of the implantation dose. The effect of indium doping in CdS films is also given for comparison. In these films, we observed that the In atoms were doped interstitially into the CdS rather than substitutionally. Here, also, the bandgap values decreased from 2.39 to 2.30 eV with the increase in In doping concentration. On implantation of both types of ions, the Raman peak position appeared at 299 cm−1, and the full width at half maximum changed with the ion dose. The results are discussed on the basis of ion implantation induced lattice damage, which implies that ion implantation can be applied to tailor-make the properties of this important semiconductor.