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DS: Fachverband Dünne Schichten
DS 16: Layer Properties: Electrical, Optical, and Mechanical
DS 16.4: Vortrag
Dienstag, 8. März 2016, 10:15–10:30, H11
Resonance X-ray reflectivity — a tool to extract chemical and valence profiles and its application to SmB6. — •Volodymyr Zabolotnyy1, Katrin Fürsich1, Robert Green2, Abdul Tcakaev1, Ronny Sutarto3, Feizhou He3, Maurits Haverkort4, Dmytro Inosov5, and Vladimir Hinkov1 — 1Universität Würzburg — 2UBC, Vancouver, Canada — 3CLS, Saskatoon, Canada — 4MPI-CPS, Dresden — 5TU Dresden
SmB6 is a renowned example of a Kondo (mixed valent) insulator. The recently proposed topologically protected surface state upgraded SmB6 to being likely the first topological Kondo insulator, and thus renewed interest in the material, particularly in the Sm2+ to Sm3+ ratio at the sample surface.
To address this question we combine cluster calculations, providing optical constants for different Sm valences, with x-ray reflectivity measurements — an established method for a non-destructive analysis of heterostructures with high probing depth (∼100 nm) and element/valence sensitivity on a nm-scale. Here we report detailed atomic and valence profiles for in situ cleaved single crystals of SmB6, which ensures clean surfaces with negligible traces of air-related contaminants. As the analysis of in-air prepared surfaces is known to be hampered by an uncontrolled built up of a contamination layer that may render reconstruction of chemical profiles very ambiguous, or even modify the surface via unwanted doping, etc., the well controlled surface chemistry proves to be a crucial aspect of the current study.