Tailoring Vanadium Dioxide Film Orientation using Nanosheets: A Combined Microscopy, Diffraction, Transport and Soft X-ray in Transmission Study

TL;DR

This study demonstrates precise control of vanadium dioxide thin film orientation on substrates using nanosheets, enabling high-quality films suitable for advanced electronic and imaging applications.

Contribution

It introduces a novel nanosheet-assisted heteroepitaxy method to tailor VO2 film orientation with high phase purity and functional quality.

Findings

Controlled VO2 orientations achieved on different substrates.

High-quality VO2 films with properties comparable to epitaxial films.

Local manipulation of VO2 orientations demonstrated on patterned nanosheets.

Abstract

VO2 is a much-discussed material for oxide electronics and neuromorphic computing applications. Here, heteroepitaxy of vanadium dioxide (VO2) was realized on top of oxide nanosheets that cover either the amorphous silicon dioxide surfaces of Si substrates or X-ray transparent silicon nitride membranes. The out-of-plane orientation of the VO2 thin films was controlled at will between (011)M1/(110)R and (-402)M1/(002)R by coating the bulk substrates with Ti0.87O2 and NbWO6 nanosheets, respectively, prior to VO2 growth. Temperature dependent X-ray diffraction and automated crystal orientation mapping in microprobe TEM mode (ACOM-TEM) characterized the high phase purity, the crystallographic and orientational properties of the VO2 films. Transport measurements and soft X-ray absorption in transmission are used to probe the VO2 metal-insulator transition, showing results of a quality equal to those from epitaxial films on bulk single-crystal substrates. Successful local manipulation of two different VO2 orientations on a single substrate is demonstrated using VO2 grown on lithographically-patterned lines of Ti0.87O2 and NbWO6 nanosheets investigated by electron backscatter diffraction. Finally, the excellent suitability of these nanosheet-templated VO2 films for advanced lensless imaging of the metal-insulator transition using coherent soft X-rays is discussed.