Atomically-Smooth Single-Crystalline VO${}_2$ thin films with Bulk-like Metal-Insulator Transitions

Abstract

Atomically-abrupt interfaces in transition metal oxide (TMO) heterostructures could host a variety of exotic condensed matter phases that may not be found in the bulk materials at equilibrium. A critical step in the development of such atomically-sharp interfaces is the deposition of atomically-smooth TMO thin films. Optimized deposition conditions exist for the growth of perovskite oxides. However, the deposition of rutile oxides, such as VO${}_2$, with atomic-layer precision has been challenging. In this work, we used pulsed laser deposition (PLD) to grow atomically-smooth VO${}_2$ thin films on rutile TiO${}_2$ (101) substrates. We show that optimal substrate preparation procedure followed by the deposition of VO${}_2$ films at a temperature conducive for step-flow growth mode is essential for achieving atomically-smooth VO${}_2$ films. The films deposited at optimal substrate temperatures show a step and terrace structure of the underlying TiO${}_2$ substrate. At lower deposition temperatures, there is a transition to a mixed growth mode comprising of island growth and layer-by-layer growth modes. VO${}_2$ films deposited at optimal substrate temperatures undergo a metal to insulator transition at a transition temperature of $\sim$325 K with $\sim$10${}^3$ times increase in resistance, akin to MIT in bulk VO${}_2$.

5 pages, 4 figures, Supplementary Information with 2 pages and 1 Figure