Band Alignment Engineering at Cu2O/ZnO Heterointerfaces

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• 作者：Sebastian Siol ; Jan C. Hellmann ; S. David Tilley ; Michael Graetzel ; Jan Morasch ; Jonas Deuermeier ; Wolfram Jaegermann ; Andreas Klein
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：August 24, 2016
• 年：2016
• 卷：8
• 期：33
• 页码：21824-21831
• 全文大小：485K
• 年卷期：0
• ISSN：1944-8252

文摘

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 ΔE_VB = 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 ΔE_VB ≈ 1.5 eV, being favorable for solar cell applications.