Single‐Phase Growth, Stabilization, and Electrical Properties of B Phase VO₂ Films Grown on Mica by Reactive Magnetron Sputtering

Abstract

The VO2 metastable (B) phase is of interest for applications in temperature sensing, bolometry, and Li‐ion batteries. However, single‐phase growth of thin films of this metastable phase is a challenge because vanadium oxide exhibits many polymorphs and the VO2 stable (M1) phase is usually present as a secondary phase. Additionally, the phase transition at 350 °C in the (B) phase severely narrows the processing window for achieving phase‐pure films. Here, single‐phase growth of 5‐to 50‐nm thick VO2 (B) films on muscovite, mica, by pulsed direct‐current reactive magnetron sputtering at 400 °C is demonstrated. The films are phase‐pure and exhibit a high density of 4.05 g cm−3 and low resistivity of about 50 mΩcm at 30 °C. Increasing the film thickness to 100 nm results in a V2O5‐capped VO2 (B) film with a resistivity of 8000 mΩcm. These results indicate that the stability of the VO2 (B) phase is sensitive to in situ annealing during deposition. These findings should serve as a basis to design processes to exclusively obtain phase‐pure VO2 (B) films.

Phase Change Kinetics of Vanadium Dioxide Thin Film Prepared by Sol–Gel Deposition

“…In view of the strong chemical interaction between VO 2 and the substrate, which causes significant strain during MIT, they proposed van der Waals epitaxy as a tool to effectively alter the phase transition kinetics in VO 2 -like systems. Ekström et al further demonstrated van der Waals epitaxy of stress-free thin films of VO 2 nonlayered materials by using magnetron sputtering to grow VO 2 films on mica substrates. , Zhang et al used the differential scanning calorimetry (DSC) technique to study the transformation kinetics of tungsten-doped VO 2 nanoparticles . They combined the isoconversional kinetics with the classical nucleation kinetics model to reasonably explain the asymmetry of MIT in the heating and cooling stages caused by tungsten doping.…”