Thickness-dependent anisotropy of metal-insulator transition in (110)-VO 2 /TiO 2 epitaxial thin films

This work reports the thickness dependence of the anisotropic electronic transport in strained VO2/TiO2 (110) epitaxial thin films with the aim of exploring the strain-modulated metal-insulator transition (MIT). The MIT temperature varies from around 349 K–341 K while increasing the film thickness, which is higher than the bulk MIT temperature of ∼340 K. More importantly, the electrical transport property is anisotropic along the in-plane [100] and [1-10] directions and the anisotropy is further improved in thicker films. Using synchrotron radiation X-ray reciprocal space mapping (RSM) and atomic force microscopy, the thickness-dependent strain induces different stripe phase states in the VO2 thin films and thus the emergence of the distinctive anisotropic electronic transport in the vicinity of the MIT. These results provide a better understanding of the crystalline-facet-dependent strain modulation of the MIT and offer a guide for designing metamaterials based on the anisotropic features of VO2 thin films.