Preparation of polycrystalline V0.97W0.03O2 thin films with ultra high TCR at room temperature

Abstract

The W doped vanadium oxide film was deposited on the SiO2 substrate by modified ion beam enhanced deposition (IBED) method. The V2O5 and WO3 mixed powders, atom ratio of W/V being 3/97, were pressed as the sputtering target. After annealed in Ar or N2 the polycrystalline IBED VO2 film doped with tungsten was obtained. The annealed IBED V0.97W0.03O2 film was orientated only to ［002］ of VO2 structure, and the latice parameter d was larger than that of VO2 crystal powder measured by X-ray diffraction. The results of resistance-temperature test showed that the phase transition temperature was decreased from 68℃ to 28℃. The thermal coefficient of resistance (TCR) was high up to 10 %/K at 300K. With the ionic radius of tungsten larger than the radius of vanadium, W6+ ion doping would induce a tension stress into the film. As a result, the transition temperature of the W-doped VO2 films was decreased to the room temperature, and the TCR was increased greatly.