L. Stan, H. Cao, X. Yan, Y. Li, W. Chen, N.P. Guisinger, H. Zhou, D.D. Fong
Argonne National Laboratory,
Keywords: VO2, graphene, remote epitaxy
Summary:Vanadium dioxide (VO2) exhibits a dramatic reversible metal-insulator transition (MIT) near room temperature. That makes it attractive for both scientific and technological applications such as transistors, optical switches, gas sensors, and smart windows. Although VO2 films have been grown by a variety of deposition techniques, precise synthesis proved to be challenging. The MIT characteristics are highly dependent of the structural quality and good stoichiometry of the films. We demonstrate an improvement in MIT characteristics of epitaxial VO2 thin films grown by using a two monolayer-thick graphene as a buffer layer placed on top of a Al2O3 (0001) substrate. Electrical transport measurements show that the on/off ratio is enhanced and the switching temperature window is narrower for VO2 thin films grown on graphene interlayer compared to those grown directly on Al2O3 substrate. With the aid of synchrotron x-ray techniques, we determined that the graphene interlayer inhibits oxygen vacancy diffusion from Al2O3 (0001) during the VO2 growth.