Atomically-smooth single-crystalline VO2 (101) thin films with sharp metal-insulator transition.

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 to grow atomically-smooth VO 2 thin films on rutile TiO 2 (101) substrates. We show that an 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 comprised of island growth and layer-by-layer growth modes. VO 2 films deposited at optimal substrate temperatures undergo a sharp metal to insulator transition, similar to that observed in bulk VO 2 , but at a transition temperature of ∼ 325 K with ∼ 10 3 times increase in resistance. [ABSTRACT FROM AUTHOR]