Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 30: ZnO and Relatives I
HL 30.2: Vortrag
Dienstag, 27. März 2012, 09:45–10:00, EW 202
Surface band gap of non-polar ZnO(11-20) cleavage surfaces determined by scanning tunneling spectroscopy — •Philipp Ebert1, Aizhan Sabitova1, Andrea Lenz2, Sarah Schaafhausen1, Lena Ivanova2, Mario Daehne2, Axel Hoffmann2, Rafal E. Dunin-Borkowski1, and Holger Eisele2 — 1Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Germany — 2Institut für Festkörperphysik, Technische Universität Berlin, Germany
The energetic position of intrinsic surface states and the size of the surface band gap on non-polar ZnO surfaces are highly debated. Therefore, we investigated the electronic properties of ZnO(11-20) cleavage surfaces by scanning tunneling microscopy. Since all previous STM measurements were done on sputter and annealed surface having high defect concentrations, we focus on highly stepped cleavage surface. Scanning tunneling spectroscopy yields that in addition to the classical tunnel current arising from electrons tunneling out or into the valence and conduction bands, respectively, a significant defect-related tunnel current exists. The defect related tunnel current arises from step-induced gap states that lead to an apparent narrowing of the band gap. The measurements indicate that no intrinsic surface states are in the fundamental band gap and the surface band gap is identical to the bulk band gap.