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O: Fachverband Oberflächenphysik
O 74: Poster Session VI: Oxide and insulator surfaces: Structure, epitaxy and growth II
O 74.4: Poster
Wednesday, March 3, 2021, 13:30–15:30, P
XPS and UPS investigation of an ALD prepared Al2O3/ZnO heterojunction — •Christoph Janowitz1, Ali Mahmoodinezhad1, Franziska Naumann2, Paul Plate2, Karsten Henkel1, and Jan Ingo Flege1 — 1Brandenburg University of Technology Cottbus-Senftenberg, K.-Zuse-Str. 1, 03046 Cottbus, Germany — 2SENTECH Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany
The band alignment of two large band gap oxides was studied by a combination of XPS and UPS using consecutive sputter steps to unravel the electronic structure and elemental composition of each layer and the interface region. An Al2O3/ZnO heterointerface (10 nm Al2O3 on 59 nm ZnO) was grown on top of a Si single crystal substrate by consecutive thermal and plasma-assisted atomic layer deposition (ALD) respectively. The valence band maximum of Al2O3 was found to be 1.1 eV below that of ZnO, the conduction band minimum 2.3 eV above, resulting in a type-I staggered heterojunction. A reduction of ZnO to elemental Zn in the interface region was detected by the apparent shoulder of the Zn 2p and 2s core levels and by the Zn LMM Auger. This suggests an ALD interface formation mechanism different from previous models identified for other heterointerfaces.