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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.46: Poster

Freitag, 4. März 2005, 17:00–20:00, Poster TU D

Investigation of the La_0.7Sr_0.3MnO₃/SrTiO₃(100)-interface by X-ray photoelectron spectroscopy under optical excitation — •Elke Beyreuther¹, Stefan Grafström¹, Christian Thiele², Kathrin Dörr², and Lukas Eng¹ — ¹Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden — ²IFW Dresden, Postfach 270116, D-01171 Dresden

The functional properties (conductivity, spin polarisation) of layered perovskite structures are crucially influenced by the electronic state distribution at internal interfaces.

The shift of an X-ray photoelectron spectrum under simultaneous optical excitation in the ultraviolet and visible range is equivalent to a surface photovoltage (SPV) and hence provides information about electronic surface and interface states, barrier heights and relaxation times. So far, semiconductor surfaces as well as the interface between organic films and semiconducting or metallic substrates have been characterized succesfully by the technique [1].

Here, we report on SPV measurements on epitaxially grown 15 nm thick La_0.7Sr_0.3MnO₃ layers on undoped and Nb-doped SrTiO₃(100) substrates. The plot of the SPV versus the excitation wavelength reflects the absorption characteristics of the substrate and reveals a continuous distribution of interface states in the sub-bandgap range. The interpretation of the results within the Schottky theory of classical metal-semiconductor contacts is discussed critically.

[1] S. Teich et al., Surf. Sci. 552, 77-84 (2004)