Berlin 2008 – wissenschaftliches Programm

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SYNF: Symposium Ferroic materials and novel functionalities

SYNF 3: Ferroic materials and novel functionalities III - Poster (joined by O posters)

SYNF 3.2: Poster

Dienstag, 26. Februar 2008, 18:30–19:30, Poster F

HX-PES study of LaAlO₃/SrTiO₃ heterostructures — •Götz Berner¹, Andreas Müller¹, Stefan Thiel², Christof Schneider², Michael Sing¹, Jochen Mannhart², and Ralph Claessen¹ — ¹Experimentelle Physik IV, Universität Würzburg — ²Experimentelle Physik VI, Universität Augsburg

Oxide heterostructures are of special interest due to the unexpected new physics occurring at the interface. E.g., a quasi-two-dimensional electron gas (2DEG), which even becomes superconducting at lowest temperatures forms at the interface of the two band insulators LaAlO₃/SrTiO₃, if at least 4 unit cells of LaAlO₃ are grown on TiO₂ terminated SrTiO₃.

In principle, angle dependent hard x-ray photoemission spectroscopy (HX-PES) is a powerful tool to get insight in both the change in chemical state and the vertical distribution of the additional charge at the interface by probing the intensity ratio of the Ti³⁺ 2p and Ti⁴⁺ 2p core lines. However, first measurements surprisingly did not show any Ti³⁺ 2p signal for various detection angles. This is in sharp contrast to the expectation from simple electrostatic considerations and recent estimates from SXRD measurements. Both claim an area carrier density corresponding to 0.5 electron per unit cell. In contrast, our HX-PES measurements indicate a much lower carrier concentration consistent with Hall measurements on our samples. As possible explanation for these discrepancies we discuss the effects of the finite LaAlO₃ thickness and the oxygen defects at the interface.