2, SIsom Thin Films LLC, Orlando, Florida, United States
Vanadium Oxide is well established for use in infrared bolometers because of its high temperature coefficient of resistivity (TCR). The metal-to-insulator transition of VO2 has attracted recent interest for switchable infrared plasmonic devices. We demonstrate VOx nanocrystalline thin films grown by aqueous spray deposition, which allows perfectly conformal coatings for convenient fabrication of (e.g.) plasmonic slot waveguides and metasurfaces. X-ray diffraction analysis shows that samples annealed post-growth in nitrogen have composition VOx with x close to 2, while X-ray photoelectron spectroscopy on this film gives an x value of about 1.5. Its measured TCR is as high as -2.7 %/degC, which compares favorably with traditional sputtered films. Samples annealed in air have higher crystallinity in the more-oxidized insulating phases V4O9 and V2O5. Thus, for phase change applications, the degree of crystallinity can be increased, and value of x tuned, by post-growth annealing in oxidizing or reducing atmospheres.