Step-like resistance changes in VO2 thin films grown on hexagonal boron nitride with in situ optically observable metallic domains.

Vanadium dioxide (VO2) thin films grown on hexagonal boron nitride (hBN) flakes show three orders of magnitude resistance change due to metal–insulator transition (MIT). The MIT property of VO2 thin films is strongly dependent on the metallic domain size, which should be identified to derive the resistance change owing to the single metallic domain. In this study, we investigated the relationship between the metallic domain size and the device-size-dependent MIT property of VO2 thin films grown on hBN. We observed by temperature-dependent Raman spectroscopy and optical microscopy the emergence of the metallic domains and determined the metallic domain size in VO2 thin films grown on hBN. The metallic domain size of the VO2 thin films grown on hBN was determined to be ∼500 nm on average in length and up to sub-micrometer scale. Electric transport measurements revealed that VO2/hBN microwires exhibit multi-level step-like resistivity changes that change by one to two orders when the length and width are ∼2 μm owing to the confined metallic domains in the micrometer scale. Our results open a way for VO2 devices, showing a steep and large resistance change even in the micrometer scale. [ABSTRACT FROM AUTHOR]