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HL: Fachverband Halbleiterphysik
HL 29: Poster Session: Spintronics; Spin-controled transport; Topological insulators; Interfaces / Surfaces; Magnetic semiconductors
HL 29.22: Poster
Montag, 11. März 2013, 16:00–20:00, Poster A
Surface modification of ZnO bulk single crystals in vacuum — •Lennart Fricke1, Tammo Böntgen1, Jan Lorbeer2, Jörg Lenzner1, Rüdiger Schmidt-Grund1, and Marius Grundmann1 — 1Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig — 2Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstr. 15, 04318 Leipzig
We discuss the modification of the surface of ZnO bulk single crystals under different environmental conditions. For that purpose, in-situ and ex-situ spectroscopic ellipsometry (SE) have been applied to get access to thin surface layers and the bulk as well as the surface near dielectric function. Ambient Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used ex-situ to characterize the surface morphology and the electrical properties of the surface.
Commercial ZnO single crystals where pre-treated to exhibit atomically flat terraces with unit cell step heights. During exposition to low pressure conditions between 1 mbar and 10−2 mbar for 2 hours, a considerable change in the SE data was observed, revealing a irreversible change in the optical thickness of the surface near region of the samples. Applying lower pressure (<10−3 mbar) or nitrogen atmosphere, no change in the optical response was detected. In all cases, no distinct change in the surface morphology or AFM phase contrast have been observed. The change of SE data can be explained by adsorption or a structural rearrangement, that is hindered by the presence of adsorbates or surface water in atmospheric air, both leading to a change in the electronic configuration of the surface.