Vanadium oxide films: High temperature fabrication, analysis and energy transfer

Vanadium oxides are widely used in industry as catalysts for variety of chemical processes such as NOx reduction, production of important chemical reagents such as sulfuric acid and synthetic fuel production. Among the vanadium oxides, some of them exhibit sharp change in resistivity above certain temperature threshold that accompanied with sharp change in reflectivity at IR region. This change in resistivity has a great potential and many applications in industry such as smart windows, memory devices and etc.

The challenge of synthesis Vanadium oxides lies in the wide variety of stable oxides which formed during deposition, and even within the same oxidation state there several different phases. In this work we have focused on interplay between temperature, flow rate, gas phase and surface chemistry that lead to formation of different phases and oxidation states of vanadium oxide with emphasis on VO₂(M) fabrication.

Specifically, via applying Chemical Vapor Deposition (CVD) technique, in this work a comprehensive screening of the effect of different conditions on final Vanadium oxide phase has been performed. Factors such as temperature and distance from evaporation source are the "handles" for controlling the final oxidation state and phase of the product. XRD patterns of the fabricated films were compared to determine phase and oxidation state of the final product. In addition a resistance measurement over temperature range of 25-100 ^oC has been done to characterize the Mott transition.

Molecular Beam Scattering (MBS) experiments of fabricated VO2(M) films with vibrationally excited NO molecules were conducted to study fingerprints of vibrational energy exchange with the solid film below and above the Mott transition.