First synthesis of vanadium dioxide by ultrasonic nebula-spray pyrolysis

Vanadium dioxide synthesis is a special problem from any precursor material due to the multi-valence nature of vanadium oxides and the fact that, among these oxides, VO2 is one of the most unstable of them. Its synthesis therefore must be done under properly controlled conditions. This paper reports on the results of the production of the sub-micrometer structured VO2 thin films for the first time by the ultrasonic nebula-spray pyrolysis from the precursor vanadium tri-chloride in an aqueous solution of 0.085 M ammonium meta-vanadate. The optimized flow rate of the argon carrier gas was 11 ml min−1 and VO2 was obtained at deposition temperature well above 600 °C. Infrared switching confirms the VO2 transition temperature in the neighborhood of 60 °C for samples prepared under argon whereas, those prepared under oxygen show a drastic shift in transition temperature to the neighborhood of room temperature (23 °C).