Microstructure and Photo-absorption Property of V-doped Nano-TiO2 Thin Films

V-doped nano-TiO2 thin films with different V-dopings were prepared by magnetron sputtering method. The microstructure observation and crystallization mechanism of the films were performed by scanning electron microscope￡¨SEM￡ and X-ray diffractometer(XRD). Raman spectrum and UV-vis transmittance spectrum of the films were also accomplished by Raman spectrometer and ultraviolet-visible spectrometer. The stress in crystal lattice and photo-absorption property of the films were studied. The results indicate that vanadium dopant in nano-TiO2 thin films can induce the oriented crystallization of TiO2 and form sizable dumbbell-state crystal grains. The addition of vanadium to TiO2 thin films suppresses the expanding of crystal lattice and the generation of rutile. The stress in the V-doped nano-TiO2 films increases with the increase of vanadium content. With the addition of vanadium, the energy level of conduction band of the nano-TiO2 lowers and stretches to bandgap. Thus the bandgap of nano-TiO2 is narrowed down. As a result, the optical absorption edge of the V-doped nano-TiO2 thin films shifts from ultraviolet zone to visible one, enhancing the absorptivity of the films on visible light.