Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO₂ Nanotubes

Scott, Jonty I, Adams, Ryan L, Martinez-Gazoni, Rodrigo F, Carroll, Liam R, Downard, Alison J, Veal, Tim D ORCID: 0000-0002-0610-5626, Reeves, Roger J and Allen, Martin W (2023) Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO₂ Nanotubes. SMALL, 19 (28). e2300520-.

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Abstract

Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO₂ nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r- and a-plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X-ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X-ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor-like states produced by the hydroxylation of the surface and is sustained at temperatures above 400 °C by the formation of in-plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO₂ nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.

Item Type:	Article
Uncontrolled Keywords:	2D electron gas (2DEG), oxygen vacancies, square nanostructures, surface hydroxyl, tin dioxide
Divisions:	Faculty of Science and Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	02 Jun 2023 07:04
Last Modified:	19 Oct 2023 09:24
DOI:	10.1002/smll.202300520
Open Access URL:	https://doi.org/10.1002/smll.202300520
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3170782