Effect of 100 MeV Nickel Ion Beam Irradiation on CdTe Nanostructured Thin Films

Irradiation by energetic ion beam at energies of the order of 100 MeV/amu is a novel technique of a thermal annealing. In the present investigation nanocrystalline CdTe thin films are irradiated with 100 MeV Ni ion beam at various fluences. During irradiation the energetic ion beam deposits all its energy to the target via electronic energy loss along its trajectory. This temporal and spatial deposition of high energy leads to heating of the thin film. This leads to the change in the surface morphology, structural and optical properties of the film. In the present work X-ray diffraction (XRD) analysis is carried out to investigate the structural changes induced by the ion irradiation. XRD studies reveal that the grain size decreases after irradiation with increasing fluence. However the cubic phase of the as-deposited film does not change after irradiation. The fragmentation of grains is also inferred from Scanning Electron Microscopy (SEM). The effect of irradiation on optical properties is studied by UV-Vis spectroscopy. The optical band gap value of as-deposited film is found to be 1.5 eV which increases after irradiation with increasing fluence. The increase in optical bandgap value is attributed to the decrease in grain size after irradiation.