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Band Alignment Engineering at Cu2O/ZnO Heterointerfaces

Siol, Sebastian and Hellmann, Jan C. and Tilley, S. David and Graetzel, Michael and Morasch, Jan and Deuermeier, Jonas and Jaegermann, Wolfram and Klein, Andreas (2016):
Band Alignment Engineering at Cu2O/ZnO Heterointerfaces.
8, In: ACS Applied Materials & Interfaces, (33), pp. 21824-21831, ISSN 1944-8244, [Online-Edition: http://doi.org/10.1021/acsami.6b07325],
[Article]

Abstract

Energy band alignments at heterointerfaces play a crucial role in defining the functionality of semiconductor devices, yet the search for material combinations with suitable band alignments remains a challenge for numerous applications. In this work, we demonstrate how changes in deposition conditions can dramatically influence the functional properties of an interface, even within the same material system. The energy band alignment at the heterointerface between Cu2O and ZnO was studied using photoelectron spectroscopy with stepwise deposition of ZnO onto Cu2O and vice versa. A large variation of energy band alignment depending on the deposition conditions of the substrate and the film is observed, with valence band offsets in the range ΔEVB = 1.45–2.7 eV. The variation of band alignment is accompanied by the occurrence or absence of band bending in either material. It can therefore be ascribed to a pinning of the Fermi level in ZnO and Cu2O, which can be traced back to oxygen vacancies in ZnO and to metallic precipitates in Cu2O. The intrinsic valence band offset for the interface, which is not modified by Fermi level pinning, is derived as ΔEVB ≈ 1.5 eV, being favorable for solar cell applications.

Item Type: Article
Erschienen: 2016
Creators: Siol, Sebastian and Hellmann, Jan C. and Tilley, S. David and Graetzel, Michael and Morasch, Jan and Deuermeier, Jonas and Jaegermann, Wolfram and Klein, Andreas
Title: Band Alignment Engineering at Cu2O/ZnO Heterointerfaces
Language: English
Abstract:

Energy band alignments at heterointerfaces play a crucial role in defining the functionality of semiconductor devices, yet the search for material combinations with suitable band alignments remains a challenge for numerous applications. In this work, we demonstrate how changes in deposition conditions can dramatically influence the functional properties of an interface, even within the same material system. The energy band alignment at the heterointerface between Cu2O and ZnO was studied using photoelectron spectroscopy with stepwise deposition of ZnO onto Cu2O and vice versa. A large variation of energy band alignment depending on the deposition conditions of the substrate and the film is observed, with valence band offsets in the range ΔEVB = 1.45–2.7 eV. The variation of band alignment is accompanied by the occurrence or absence of band bending in either material. It can therefore be ascribed to a pinning of the Fermi level in ZnO and Cu2O, which can be traced back to oxygen vacancies in ZnO and to metallic precipitates in Cu2O. The intrinsic valence band offset for the interface, which is not modified by Fermi level pinning, is derived as ΔEVB ≈ 1.5 eV, being favorable for solar cell applications.

Journal or Publication Title: ACS Applied Materials & Interfaces
Volume: 8
Number: 33
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Surface Science
Profile Areas
Profile Areas > Thermo-Fluids & Interfaces
Date Deposited: 28 Aug 2016 15:09
Official URL: http://doi.org/10.1021/acsami.6b07325
Identification Number: doi:10.1021/acsami.6b07325
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