Tunable hysteresis in metal-insulator transition of nanostructured vanadium oxide thin films deposited by reactive direct current magnetron sputtering

摘要

Nanostructured vanadium oxide (nano-VOx) films were deposited at low temperature on glass substrates by reactive direct current (DC) magnetron sputtering followed by in-situ annealing process. The chemical compositions, crystal structures, morphologies and metal-insulator transition (MIT) properties of nano-VOx films were investigated. The experimental results indicate that deposition conditions (reactive O_2 gas flow rates, annealing temperatures and annealing times) have important effects on film morphologies (grain shapes and grain sizes) which profoundly affect the MIT properties of VOx films, especially the hysteresis width. The film consisting of spheroidal small particles shows a large hysteresis width due to the small density of nucleating defects and large interfacial energies, whereas the film consisting of the misshapen and/or large particles shows a small hysteresis width due to the large density of nucleating defects. These experimental results suggest that reactive DC magnetron sputtering is an effective process for preparing high-quality thermochromic nano-VOx films with tunable hysteresis widths and surface morphologies.