Influence of nitrogen implantation on the structural and optical properties of CdS thin films

The effects of nitrogen-ion implantation on vacuum-evaporated cadmium sulphide (CdS) thin films were investigated using X-ray diffraction (XRD), optical transmittance spectra, and Raman scattering studies. X-ray diffraction studies revealed that the as-deposited CdS films had a hexagonal structure with a preferential (002) orientation. The XRD patterns revealed formation of Cd metallic clusters in the ion-implanted films. The band gap of the N⁺-implanted films decreased from 2.385 eV for the as-deposited film to 2.301 eV for maximum implantation whereas the optical absorption coefficient values increased with increasing implantation dose. Raman scattering due to the A_l(LO) phonon was observed at 299 cm^-1 in the as-deposited CdS film with a large full width at half maximum (FWHM). The Raman peak position did not change much whereas the FWHM increased with the ion dose. These are attributed to the effect of implantation induced lattice damage. A decrease in the area of the Raman peak of the CdS A_l(LO) mode is seen on implantation.