Study Of The Structure And Photocatalytic Activity Of Doping TiO₂ Thin Films Deposited By Electron Beam Evaporation

Over past few years, TiO2 as one of the optoelectronic functional materials with a high response to UV and visible light is of interest due to non-toxic, the thermal stability, the high photocatalytic activity. However, the large scale application of TiO2 thin film as mutual photocatalyst is hampered by the wide band-gap and higher recombination rate of photo-generated electrons and holes. To effectively improve the use of visible and reduce electron-hole recombination rate, great efforts have been made to modify of TiO2.In this work, La-TiO2 thin films were deposited by electron beam evaporation method. The effect of doping concentration, substrate material and annealing temperatures on phase transition, the structure and surface morphology of La-TiO2 thin films has been investigated. The surface morphology, the crystal structure and the component of the films were characterized by Raman, XRD, AFM, and XPS. To analysis the effect of doping different materials ions on the visible absorption range of La-TiO2 thin films, UV-Vis spectroscopy was used to test optical properties of films. The results revealed that an appropriate La doping could enhance the thermal stability and improve the phase transition temperature. With the different doping concentration and substrate materials, the morphology of La-TiO2 films changes greatly. Compared to the TiO2 thin films, the gap adsorption edge of La-TiO2 films exhibited a little red shift and slightly narrowed their band gaps. It is found that the gain size of La-TiO2 film is the smallest and the band gap is the narrowest among the films when the mass ratio of La3+ to TiO2 is 5wt% with (004) preferential growth orientation which are in good agreement with the vibration modes of TiO2 in anatase phase annealed at 600℃.Si-TiO2 thin films were also prepared by the same method. The influence of substrate material and annealing temperatures on phase transition, the structure and surface morphology of Si-TiO2 thin films were analyzed. The experiment results suggested that the annealing temperature has a strong effect on the structure and morphology of Si-TiO2 films. And the enhanced thermal stability of Si-TiO2 films enabled them to elevate the phase transformation temperature.The photocatalytic activity of La-TiO2 and Si-TiO2 films was examined on the degree of degradation of rhodamine B in aqueous solution with UV illumination. The impact of under the different light source, different initial rhodamine B concentration, and the preparation technical conditions on the photocatalyst activity has been systemically studied.