Effect of 80 MeV oxygen ion beam irradiation on the properties of CdTe thin films

Polycrystalline CdTe thin films were irradiated with 80 MeV oxygen (O6+) ions for various fluences and its effect on the composition, structure, surface topography and optical properties have been investigated. The asgrown films are found to be slightly Te-rich in composition and there is no significant change in the composition after irradiation. X-ray diffraction analysis shows a high degree of crystallite orientation along the (111) plane of cubic phase CdTe. Upon irradiation a large decrease in intensity of the (111) plane and a small shift in the peak position has been resulted. The shift in the peak position is correlated with the change in the residual stress. The surface roughness of the films get increased after irradiation. A decrease in the grain size was observed after irradiation due to ioninduced recrystallization. The optical band gap energy decreased from 1.53 eV for as-grown film to 1.46 eV upon irradiation. The photoluminescence (PL) spectrum is dominated by the defect band and the effect of irradiation has been discussed and correlated with the observed change in the XRD peak position and optical band gap.