Hydrothermal epitaxy growth of self-organized vanadium dioxide 3D structures with metal–insulator transition and THz transmission switch properties

Abstract

The hydrothermal method is the most effective approach for the synthesis of VO₂ metastable polymorphs with unique powder crystallite morphology. In this work, we expanded the capabilities of this method, directing it to the growth of oriented crystallites in self-organized systems on single crystal substrates. According to our investigations, a large variety of 3D structures of vanadium dioxide can be obtained using one single crystal substrate r-sapphire by fine tuning of synthesis parameters. The orientation growth of six-pointed vanadium dioxide crystallites fits into an epitaxial growth model describing unit cell relations between the VO₂(M₁) film and r-sapphire substrate. We describe the process of VO₂(M₁) phase stabilization in the films and the changes of resistivity and terahertz transparency of the films based on the metal–insulator transition (MIT).