Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 16: Correlated Electrons: Low-dimensional Systems - Materials 1
TT 16.10: Vortrag
Dienstag, 24. März 2009, 12:15–12:30, HSZ 304
Profiling the interface electron gas of LaAlO3/SrTiO3 heterostructures by hard X-ray photoelectron spectroscopy — •G. Berner1, M. Sing1, K. Goß1, A. Wetscherek1, A. Müller1, A. Ruff1, S. Thiel2, J. Mannhart2, S.A. Pauli3, C.W. Schneider3, P.R. Willmott3, and R. Claessen1 — 1Experimentelle Physik IV, Universität Würzburg — 2Experimentelle Physik VI, Universität Augsburg — 3Paul Scherrer Institut, CH-5232 Villingen, Switzerland
Oxide heterostructures are of special interest due to unexpected new physics occurring at the interface. One heavily discussed topic is the quasi-two-dimensional electron gas (2DEG), which emerges at the interface of the two band insulators LaAlO3/SrTiO3, if at least 4 unit cells of LaAlO3 are grown on TiO2-terminated SrTiO3. Moreover, both a magnetic and a superconducting phase at low temperatures have been reported for the ground state of the 2DEG. We have studied this buried interface by angle dependent hard x-ray photoemission spectroscopy (HAXPES), which is a powerful tool to get insight in both change in chemical state and vertical distribution of the additional charge at the interface. The distinct angle-dependence of the intensity ratio of the Ti3+ 2p and Ti4+ 2p core lines indicates that the thickness of the 2DEG is much smaller than the HAXPES probing depth of 4 nm. It is observed that the carrier density varies between differently prepared heterostructures and increases with increasing numbers of LaAlO3 overlayers. Our results point to electronic reconstruction in the overlayer as driving mechanism for the 2DEG formation and is supportive for the recently observed 2D superconductivity.