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Electroreduction of Aryldiazonium Ion at the Polar and Non-Polar Faces of ZnO: Characterisation of the Grafted Films and Their Influence on Near-Surface Band Bending.

Authors :
McNeill AR
Martinez-Gazoni R
Reeves RJ
Allen MW
Downard AJ
Source :
Chemphyschem : a European journal of chemical physics and physical chemistry [Chemphyschem] 2021 Jul 02; Vol. 22 (13), pp. 1344-1351. Date of Electronic Publication: 2021 May 28.
Publication Year :
2021

Abstract

ZnO is a strong candidate for transparent electronic devices due to its wide band gap and earth-abundance, yet its practical use is limited by its surface metallicity arising from a surface electron accumulation layer (SEAL). The SEAL forms by hydroxylation of the surface under normal atmospheric conditions, and is present at all crystal faces of ZnO, although with differing hydroxyl structures. Multilayer aryl films grafted from aryldiazonium salts have previously been shown to decrease the downward bending at O-polar ZnO thin films, with Zn-O-C bonds anchoring the aryl films to the substrate. Herein we show that the Zn-polar (0001), O-polar (000 1 ‾ ), and non-polar m-plane (10 1 ‾ 0) faces of ZnO single crystals, can also be successfully electrografted with nitrophenyl (NP) films. In all cases, X-ray photoelectron spectroscopy (XPS) measurements reveal that the downward surface band bending decreases after modification. XPS provides strong evidence for Zn-O-C bonding at each face. Electrochemical reduction of NP films on O-polar ZnO single crystals converts the film to a mainly aminophenyl layer, although with negligible further change in band bending. This contrasts with the large upward shifts in band bending caused by X-ray induced reduction.<br /> (© 2021 Wiley-VCH GmbH.)

Details

Language :
English
ISSN :
1439-7641
Volume :
22
Issue :
13
Database :
MEDLINE
Journal :
Chemphyschem : a European journal of chemical physics and physical chemistry
Publication Type :
Academic Journal
Accession number :
33942472
Full Text :
https://doi.org/10.1002/cphc.202100240