Phase stabilization of VO₂ thin films in high vacuum

A new growth approach to stabilize VO₂ on Al₂O₃ in high vacuum is reported by reducing vanadium oxytriisopropoxide (VTIP) with vanadium metal. Phase stabilization and surface wetting behavior were studied as a function of growth parameters. The flux balance of VTIP to V in combination with growth temperature was identified to be critical for the growth of high quality VO₂ thin films. High V fluxes were required to suppress the island formation and to ensure a coalesced film, while too high V fluxes ultimately favored the formation of the undesired, epitaxially stabilized V₂O₃ phase. Careful optimization of growth temperature, VTIP to V ratio, and growth rate led to high quality single phase VO₂ thin films with >3.5 orders of magnitude change in resistivity across the metal-to-insulator transition. This approach opens up another synthesis avenue to stabilize oxide thin films into desired phases.