N-doped Tungsten Dioxide Vanadium Thin Films

Scientists discovered that VO₂ has a distinctive phase change function long time ago. When the phase transition temperature is 68°C, it can change reversibly from low temperature monoclinic system to high temperature tetragonal system.

The physical properties such as resistivity, optical transmittance, permeability and so on have changed greatly. Doping method is an effective method to change the phase transition temperature of VO₂. The preparation methods of doped VO₂ films include sol-gel doping method, hydrothermal synthesis doping method, sputtering doping method, metal organic compound vapor deposition doping method, pulse laser deposition process, inorganic sol-gel doping method, and microwave plasma method. We prepare it by microwave plasma method.

Another main content of the preparation of doped VO₂ thin film is the selected doping compounds. Weigh a certain amount of pure V₂ O₅ powder and W₂O₃ into the pot, then stirring, put in the muffle furnace and under the air medium, heating to 900°C to melt. After 15 min of heat preservation, the molten solution is quickly poured into a certain amount of deionized water to quench and stir violently until a stoichiometric V_1.96W_0.04O₅ sol is formed. The prepared V_1.96W_0.04O₅ sol has been plated on glass sheets cleaned with 75% alcohol and deionized water by spin coating method. Dry naturally at the ventilation, then obtain synthesis of stoichiometric V_1.96W_0.04O₅ thin films.

The V_1.96 W_0.04O₅ films have been prepared by microwave plasma enhanced method, control reaction parameters, the V_1.96W_0.04O₅ thin film was reduced to V_0.98W_0.02O₂ and doped with nitrogen. The reaction time was 10~30 min. The V_0.98W_0.02O₂-x N y thin film was obtained.

The phase transition temperature of VO₂ powders can be reduced by VO₂ film, which is about 6°C, with the addition of nitrogen and tungsten ions, the phase transition temperature of V_0.98W_0.02O₂ -x N y thin film can be effectively reduced, when the nitrogen flow rate is changed, the phase transition temperature of vanadium tungsten dioxide thin film can be reduced to 35°C at minimum. This is the closest phase change material known to be the daily temperature.

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