Influence of film thickness on texture and electrical and optical properties of room temperature deposited nanocrystalline V2O5 thin films

Nanocrystalline V2O5 thin films have been grown at low temperature on glass substrates by dc magnetron sputtering using a vanadium metal target. Film thickness was found to have a great impact on the orientation, shape, and size of the crystallites of these films. X-ray diffraction (XRD) patterns of the films with a thickness of 110 nm show a strong c-axis orientated crystal structure with a preferred (001) orientation, while those with a thickness of 315 nm show mixed orientations (a-axis+c-axis). With further increase in film thickness, an a-axis orientation with predominant (200) reflection was observed in the XRD pattern. The shape of the crystallite changes from a rodlike to a bricklike structure with change in crystallographic orientation from (001) to (200). Atomic force microscopy results were also in agreement with the field emission scanning electron microscopy and XRD results. A direct correlation has been established between the semiconductor to metal transformation of V2O5 films and their crystallite size and orientation. The optical measurement also revealed a systematic band gap variation (from 2.50 to 2.20 eV) with variation in film thickness. (c) 2008 American Institute of Physics.