Inhomogeneous electronic state near the insulator-to-metal transition in the correlated oxide VO2

We investigate the percolative insulator-to-metal transition (IMT) in films of the correlated material vanadium dioxide (VO2). Scattering-type scanning near-field infrared microscopy and atomic force microscopy were used to explore the relationship between the nucleation of metallic regions and the topography in insulating VO2. We demonstrate that the IMT begins within 10 nm from grain boundaries and crevices by using mean curvature and statistical analysis. We also observe coexistence of insulating and metallic domains in a single crystalline grain that points to intrinsic inhomogeneity in VO2 due to competing electronic phases in the IMT regime.