Microstructure and Photo-absorption Property of V-doped Nano-TiO_2 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.