Nanoscale self-templating for oxide epitaxy with large symmetry mismatch

TL;DR

This study reveals how a nanoscale interfacial bi-layer facilitates the epitaxial growth of strain-free VO2(B) on SrTiO3 despite large symmetry and lattice mismatches, using advanced microscopy techniques.

Contribution

It uncovers a nanoscale self-templating mechanism involving an interfacial bi-layer that enables epitaxy across large symmetry mismatches.

Findings

Identification of a 2-3 unit cell interlayer at the interface.

The interlayer is composed of strained VO2(B) nanodomains and an extra (Ti,V)O2 layer.

The interlayer enables coherent and semi-coherent interfaces with the substrate and film.

Abstract

Direct observations using scanning transmission electron microscopy unveil an intriguing interfacial bi-layer that enables epitaxial growth of a strain-free, monoclinic, bronze-phase VO2(B) thin film on a perovskite SrTiO3 (STO) substrate. We observe an ultrathin (2-3 unit cells) interlayer best described as highly strained VO2(B) nanodomains combined with an extra (Ti,V)O2 layer on the TiO2 terminated STO (001) surface. By forming a fully coherent interface with the STO substrate and a semi-coherent interface with the strain-free epitaxial VO2(B) film above, the interfacial bi-layer enables the epitaxial connection of the two materials despite their large symmetry and lattice mismatch.