Optical Switches Based on Semiconducting Vanadium Dioxide Films Prepared by the Sol-Gel Process,
JOHNS HOPKINS UNIV LAUREL MD APPLIED PHYSICS LAB
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Vanadium dioxide thin films have been grown from vanadium tetrakis t-butoxide by the sol-gel process. A new method for the synthesis of the vanadium precursor was also developed. Films were deposited by dipcoating glass slides from an isopropanol solution, followed by postdeposition annealing of the films at 600 degC under nitrogen. The properties of these films, to a high degree, were a function of crystalline boundaries and crystalline grain size. These gel-derived V02 films undergo a reversible semiconductor-to-metal phase transition near 72 degC, exhibiting characteristic resistive and spectral switching comparable with near stoichiometric V02 films prepared on noncrystalline substrates by other techniques. Paralleling the investigation of pure V02, films were doped with hexavalent transition metal oxides to demonstrate lowering of the transition of the transition temperature.