Using a vanadium dioxide (VO2) source, highly pure and amorphous vanadium oxide (VO) thin films were deposited using an e-beam evaporator at room temperature and high vacuum (<10-7 Torr). Then, by controlling the post-annealing conditions such as N2：O2 pressure ratio and annealing time, we could easily synthesize a homogeneous VO2 thin film and also mixed-phase VO thin films, including VO2, V2O5, V3O7, V5O9, and V6O13. The crystallinity and phase of these were characterized by X-ray diffraction, and the surface morphology by FE-SEM. Moreover, the electrical properties and ethanol sensing measurements of the VO thin films were analyzed as a function of temperature. In general, mixed-phases as a self-doping effect have enhanced electrical properties, with a high carrier density and an enhanced response to ethanol. In summary, we developed an easy, scalable, and reproducible fabrication process for VO thin films that is a promising candidate for many potential electrical and optical applications.
