Swift heavy ion beam irradiation induced modifications in structural, morphological and optical properties of CdS thin films

The effect of 100 MeV Ag+7 ion irradiation on the properties of thermally evaporated CdS thin films has been investigated. The structure of the films studied is polycrystalline with a mixture of dominant hexagonal and few traces of cubic phases. A shift in the peak position due to irradiation was observed and is discussed on the basis of change in the residual stress. Annihilation of microcracks due to irradiation induced grain growth has been observed from the SEM micrographs at lower ion fluences. The optical transmittance and absorption spectra revealed a shift in the fundamental absorption edge and hence variations in the optical band gap. The band gap energy has been estimated for as-deposited and irradiated films and is found to decreases upon irradiation. A significant increase of refractive index has been observed after irradiation.