Enhancing the metal–insulator transition in VO₂ heterostructures with graphene interlayers

Studies were conducted on epitaxial VO₂ thin films to assess to the effect of remote epitaxy on the metal–insulator transition (MIT). The epitaxial VO₂ heterostructures were synthesized on both bare Al₂O₃ (0001) substrates and Al₂O₃ substrates coated with two monolayer-thick graphene. While both systems exhibit the MIT, the film grown by remote epitaxy on graphene demonstrates improved transport properties. Electrical transport measurements show that the on/off ratio is enhanced by a factor of ∼7.5 and the switching temperature window is narrower for VO₂ thin films grown on graphene. By characterizing the heterostructures with a suite of structural, chemical, and spectroscopic tools, we find that the graphene interlayer inhibits oxygen vacancy diffusion from Al₂O₃ (0001) during the VO₂ growth, resulting in improved electrical behavior at the MIT.