Tailoring Vanadium Dioxide Film Orientation Using Nanosheets: a Combined Microscopy, Diffraction, Transport, and Soft X‐Ray in Transmission Study

• Published in: Advanced functional materials 2020-01, Vol.30 (1), p.n/a
• Main Authors: Le, Phu Tran Phong, Hofhuis, Kevin, Rana, Abhimanyu, Huijben, Mark, Hilgenkamp, Hans, Rijnders, Guus A.J.H.M., ten Elshof, Johan E., Koster, Gertjan, Gauquelin, Nicolas, Lumbeeck, Gunnar, Schüßler‐Langeheine, Christian, Popescu, Horia, Fortuna, Franck, Smit, Steef, Verbeek, Xanthe H., Araizi‐Kanoutas, Georgios, Mishra, Shrawan, Vaskivskyi, Igor, Dürr, Hermann A., Golden, Mark S.
• Format: Article
• Language: English
• Subjects: Amorphous silicon; Crystal structure; Crystallography; Electron backscatter diffraction; lensless imaging; Mapping; Materials science; Metal-insulator transition; Nanosheets; Orientation; Oxygen consumption; Silicon dioxide; Silicon nitride; Silicon substrates; Temperature dependence; Thin films; transmission; Transport; Vanadium dioxide; X-ray absorption
• ISSN: 1616-301X; 1616-3028; 1616-3028
• DOI: 10.1002/adfm.201900028

Vanadium dioxide (VO2) is a much‐discussed material for oxide electronics and neuromorphic computing applications. Here, heteroepitaxy of VO2 is 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 is 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 transmission electron microscope mode (ACOM‐TEM) characterize 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. Oxide heteroepitaxy of VO2 on technical substrates is realized using pulsed laser deposition. VO2 films are grown in the (110)R and (002)R orientation using Ti0.87O2 and NbWO6 nanosheets on Si and Si3N4 membranes. Local control of VO2 orientation on the micrometer level on single, arbitrary substrates is demonstrated, and soft X‐ray experiments on the metal–insulator transition are conducted in transmission.