Studies On Microstructure And Chromogenic Performance Of Vanadium Oxides Thin Films

V2O5 and VO2 thin films are a kind of outstanding chromogenics, and have a large potential for various applications, such as display devices, light storage devices, optical switch, bolometer, smart-windows and so on. However, the device performance is greatly influenced by the morphology and structural order of the film, which in turn depend on the deposition technique and the growth parameters.V2O5 thin films with preferred (001) orientation were deposited on Si(100) substrate by reactive dc magnetron sputtering. V2O5 film could be converted to (001) oriented VO2 film after vacuum annealing process. The surface morphology, microstructure and composition of the samples were analysed using XRD, SEM, FTIR, XPS and XAS. The relationships between the physical properties of vanadium oxides films and their photoelectric properties were systematically studied.These investigations revealed that the chemical composition, deposition rate and the orientation direction of films were affected by the oxygen partial pressure. The crystallinity is improved with the increase of oxygen partial pressure. Highly nano-crystalline orientated films of V2O5 on Si(100) can be grown with a layered structure at oxygen partial pressure of 0.4Pa. The crystal grain boundary of V2O5 films was melted and disappeared as increasing the deposition temperature, and the crystalline V2O5 films can be obtained by deposition at >300℃. These films showed excellent cathode and anodic electrochromic performance at different wavelength region. Based on the results of V2O5 films measured by XPS, the chromogenic performance was explained on the binding energy structure view.The VO2 films with (001) orientation inherited the layered structure of V2O5 films, and the surface morphology was also affected by that of V2O5 films. The effect of annealing conditionsuch as temperature, time and vacuum on microstructure of VO2 films was studies. The crystalline VO2 films can be obtained after annealing at 450℃ 3 hour in 10Pa vacuum. The conductivity of films increases linearly with increasing the temperature.