Berlin 2015 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 4: Thin Film Characterisation II: Structure Analysis and Composition

DS 4.7: Vortrag

Montag, 16. März 2015, 16:30–16:45, H 0111

k-resolved electronic structure by soft-X-ray ARPES: From 3D systems to heterostructures and impurities — •V.N. Strocov, M. Kobayashi, L.L. Lev, J. Krempasky, V.A. Rogalev, U. Staub, H. Volfová, J. Minár, X. Wang, T. Schmitt, and C. Cancellieri — Swiss Light Source, Paul Scherrer Institute, Switzerland

The spectroscopic power of soft-X-ray ARPES in the energy range around 1 keV arises from enhanced photoelectron escape depth, sharp definition of 3D electron momentum k, and resonant photoexcitation delivering elemental and chemical state specificity. We demonstrate that the advanced instrumentation at the Swiss Light Source has enabled stretching this technique from 3D materials to the most photon-hungry cases of buried heterostructures and impurities [1].

One of the applications to 3D materials is the magnetoresistive 3D perovskite La_1−xSr_xMnO₃. Its experimental Fermi surface shows shadow contours manifesting the rhombohedral lattice distortion affecting the CMR. The heterostructures are illustrated with the LaAlO₃/SrTiO₃ buried interface. Exploiting resonant photoexcitation of the interface Ti3⁺ ions, we resolve different subbands of the interface quantum well states. Their spectral function reveals prominent polaronic coupling which reduces the electron mobility. An example of the impurity systems is the diluted magnetic semiconductor GaMnAs. Resonant photoexcitation at the Mn 2p edge enables identification of the ferromagnetic Mn impurity band as well as its energy alignment and mechanism of hybridization with the host GaAs bands.

[1] V.N. Strocov et al, Synchr. Rad. News 27, N2 (2014) 31