Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 79: Electronic structure II

O 79.5: Talk

Thursday, March 17, 2011, 16:00–16:15, WIL C107

localized vs. delocalized character of charge carriers in LaAlO3/SrTiO3 heterostructure — •kejin zhou¹, milan radovic^2,1, justine schlappa¹, vladimir strocov¹, ruggero frison¹, joel mesot^1,2, luc patthey¹, and thorsten schmitt¹ — ¹Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland — ²Laboratory for synchrotron and neutron spectroscopy, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland

Oxide heterostructures have been attracting great attention due to extraordinary phenomena occurring at the interface and their potential application for device design. A particularly fascinating system is the two-dimensional conductive interface between the band insulators LaAlO₃ (LAO) and SrTiO₃ (STO), which can be even driven to magnetic and superconducting phases at low temperatures. Resonant inelastic x-ray scattering at Ti L-edges is particularly suitable to address the electronic structure of its interface since the Ti³⁺ states clearly display strong dd excitations while Ti⁴⁺ states exhibit only elastic emission in the low energy loss regime. Our studies on LAO/STO superlattices prepared by pulsed laser deposition unambiguously reveal the presence of both localized and delocalized Ti 3d carriers generated during the building of the LAO/STO interfaces. Systematic studies on samples before and after annealing under O₂ atmosphere and high temperature show that the dual character carriers can be either induced by electron transfer due to the polar-discontinuity or by oxygen vacancies defects. Oxygen vacancies and electronic reconstruction are equivalent in balancing the built-up electric potential.