High-temperature optical properties of thin-film vanadium oxides -: VO2 and V2O3

Thin-film vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) undergo shear phase transformations at 340K and 120K, respectively. The electrical and infrared optical properties of these materials are dramatically impacted by this phase transformation. Below the phase transition temperature, both VO2 and V2O3 are "poor" electrical insulators and have minimal absorption in the infrared spectral region. Above the phase transition temperature, both VO2 and V2O3 are poor conductors and are opaque in the infrared. The infrared thermochromic properties of these materials make them interesting candidates for several optical applications. Utilization of either VO2 or V2O3 necessitates an accurate knowledge of the optical properties both above and below the phase transition temperature. This paper reports on some recent infrared ellipsometric measurements an the optical properties of these materials above the transition temperature. These measurements found that both are strongly dispersive through the 3-12 micron spectral region. In addition, the temperature dependence of the optical properties of VO2 above the transition temperature can be related to the film morphology and stoichiometry.