Visualization of local phase transition behaviors near dislocations in epitaxial VO₂/TiO₂ thin films

We investigated local phase transition behaviors in epitaxial VO₂/TiO₂ thin films using variable-temperature Kelvin probe force microscopy while spanning the metal-insulator transition (MIT). Fully strained thin films were almost free of grain boundaries. In contrast, thicker films had cracks (dislocations) caused by strain relaxation. The surface area fraction of the insulating phase near the dislocations was higher than that in other regions. Thicker films have complicated domain patterns; hence, the three-dimensional percolation model properly described the MIT behaviors. In contrast, the two-dimensional percolation model well explained the transition behaviors of uniformly strained thinner films.