Regensburg 2016 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 40: Topical session: In-situ Microscopy with Electrons, X-Rays and Scanning Probes in Materials Science IV - Atomic structure and defects III

MM 40.6: Talk

Wednesday, March 9, 2016, 17:45–18:00, H38

Analysis of local atomic arrangement in layered Ge-Sb-Te crystal structures by advanced scanning transmission electron microscopy — •Andriy Lotnyk, Ulrich Ross, Sabine Bernütz, Erik Thelander, and Bernd Rauschenbach — Leibniz Institute of Surface Modification (IOM), Permoserstr. 15, D-04318 Leipzig, Germany

The knowledge on the proper local atomic arrangement in Ge-Sb-Te compounds is of particular interest for optical and electronic applications such as data storage, thermoelectric and ferroelectric. In this work, we study the local atomic arrangements in Ge-Sb-Te thin films consisting of layered Ge₂Sb₂Te₅, Ge₁Sb₂Te₄ and Ge₃Sb₂Te₆ crystal structures by using state of the art atomic-resolution aberration-corrected (Cs-corrected) high-angle annular dark-filed scanning transmission electron microscopy (HAADF-STEM) and proper theoretical image simulations. The results show that the intensities in simulated Cs-corrected HAADF-STEM micrographs are very sensitive to thermal displacement factors in the studied structures at specific lattice sites. Based on these findings, we are able to determine proper stacking sequences in the Ge-Sb-Te phases by comprehensive analyses of experimental and simulated image intensities. The experimental data reveal that the Ge and Sb atomic species tend to form intermixed cation layers which differ from theoretical predictions. However, the ratio of Sb to Ge is different in distinct cation layers. The obtained data are discussed with respect to existing experimental and theoretical structure models reported for bulk Ge-Sb-Te materials.