Novel Method of Preparation of Vanadium Dioxide Thin Films
Thin films of stoichiometric vanadium dioxide are not easily prepared. In chemical vapor deposition and vacuum deposition processes, precise control of the deposition atmosphere is needed to maintain the proper chemical composition. In processes requiring post reduction of higher oxides, the films tend to be inhomogeneous and porous.
According to the invention, vanadium dioxide is prepared from a tetravalent vanadium compound using a sol-gel process. The tetravalent compound is dissolved in a solvent and is hydrolyzed and condensed to progressively form a sol, while giving off alcohol and water. As the solvent evaporates, a gel forms which is then dehydrated to form vanadium dioxide.
If a thin film is desired, an appropriate substrate is dipped into the sol. The gel forms on the substrate as it is withdrawn from the sol. The dipping process is particularly useful for the coating of large surfaces such as windows, walls and wind screens, including windshields, with a thin film of vanadium dioxide.
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