Preparation Of VO₂ Thin Films And Study The Effects Of Doping Au On Phase-Transition Properties

ABSTRACT:Vanadium dioxide (VO2)is a typical thermochromical compound. With the rise of temperature, it has Low temperature semiconductor-to-high temperature metal transition at 68℃(reversible), the phase-transition is accompanied with abrupt changes in its electrical and optical properties. This special properties make VO2 in many fields has important application value, for example, it can use as thermistor materials, optical switches, smart windows, solar temperature-control devices and so on, the important is that its transition temperature can be adjusted through doping. As a special function material, it has high value for study. This paper reported that the VO2 thin films were prepared by radio frequency reactive magnetron sputtering and optical and electrical properties of which VO2 thin films doped with Au and Au array were studied.In this paper, VO2 thin films were fabricated on the plain glass substrates and sapphire substrates by magnetron sputtering method. The curve of resistance-temperature were determined using four-point probe method; the film's resistance changed about two orders of magnitude at the transition temperature on both of glass substrates and sapphire substrates. Transmittance spectrums were measured by high UV sensitivity spectrometer in varied temperature. At 1100nm wavelengths, with the temperature rise the transmittance reduces from 35% to 15%, 20% off on the glass substrates. We found that the variation of the rate in the infrared is more obviously than in the visible light, this result approaches with the best in references.Other work of this paper, Au was doped into VO2 thin films using direct sputtering and nanosphere lithography (NSL) method, respectively. In the nano-etching method:Firstly, polystyrene colloid ball mask was prepared using drop point method; secondly, Au was sputtered on the mask board; thirdly, hexagonal Au nano-point array was obtained after removing polystyrene ball; finally, VO2 thin films was sputtered on the Au hexagonal nano-point array and Au:VO2 composite films was obtained. Both of methods reduced the phase-transition temperature, especially nano-etching method, using this method the film's phase-transition temperature has reduced from 68℃to between 37-45℃, the largest decreasing amplitude to 30℃The transmittance amplitude decreases 10%. Synchronously, we analysis the films by XRD, AFM and SEM, learn the film's physical properties under different growth conditions.