Dr. Xun Cao, Associate Professor, Shanghai Institute of Ceramics, Chinese Academy of Science, China

Title: Optical and Electrical Properties of Epitaxial VO₂ Thin Films and Device Applications

Abstract: For correlated materials, charge-spin-orbital-lattice interactions have spawned a rich variety of electronic phases. Vanadium dioxide (VO₂), an archetypal correlated oxide compound, undergoes a temperature-driven metal-insulator transition (MIT) near room temperature with a concomitant change in crystal symmetry. In VO₂ single crystals, MIT shows a sudden jump in electrical resistivity by a factor of Δρ/ρ≥10⁴, and is also accompanied by a rutile-monoclinic structural phase-transition. This sharp MIT above room temperature promises a wide range of potential applications, such as fast optoelectronic switches, Mott transistors, memristors, and artificial neuron networks. Most of these applications require low-dimensional geometries such as thin films and deliberate control of MIT dynamics at the nanoscale, including phase nucleation and evolution. In this presentation, I will talk about the most important effects of strain (tensile/compressive/free-standing) on the MIT behaviors of epitaxial VO₂ thin films. How to control the strain of thin films can benefit for the modulation of phase-transition performance of VO₂ materials. Also with the control of phase-transition behaviors, people can utilize the optical and electrical properties of VO₂ and develop potential devices. In addition, the mechanism of the phase-transition behavior in VO₂ materials is also very interesting. Realizing control of properties of VO₂ by defects modulation is an efficient route for understanding the nature of phase-transition and developing novel functional devices for practical applications.

Keywords: Correlated materials, VO₂, epitaxial growth, strain, modulation