Local atomic arrangement in Ge-Sb-Te phase-change thin films

International Conference on Applied Crystallography

October 17-19, 2016 Houston, USA

Andriy Lotnyk, Ulrich Ross, Xinxing Sun, Erik Thelander and Bernd Rauschenbach

Leibniz Institute of Surface Modification, Germany

Scientific Tracks Abstracts: J Material Sci Eng

Abstract :

Phase change materials (PCM), such as Te-based Ge2Sb2Te5 (GST), are known from optical memory applications and can be also used in non-volatile next generation random access memory. The relevant phases of GST are an amorphous phase, a metastable cubic rock salt like structure and a stable hexagonal layered structure. However, the atomic arrangements in the GST lattices are not well-understood and still under discussion. Insights into the local atomic arrangement of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view as well as for optical and electronic applications such as data storage, thermoelectric and ferroelectric. In this work, the local atomic arrangement in metastable GST and in Ge-Sb-Te thin films consisting of GST, Ge1Sb2Te4 and Ge3Sb2Te6 layered crystal structures are studied by using a combination of atomic-resolution aberrationcorrected (Cs-corrected) high-angle annular dark-filed scanning transmission electron microscopy (HAADF-STEM) and detailed theoretical image simulation approaches. By comprehensive analyses of experimental and simulated HAADF-STEM image intensities, a structural model for metastable Ge2Sb2Te5 is proposed. In addition, the proper stacking sequences in the Ge-Sb-Te phases are determined. The obtained data are discussed with respect to existing experimental and theoretical structure models reported for bulk Ge-Sb-Te materials.

Biography :

Andriy Lotnyk has completed his PhD in 2007 from the University of Halle working at the Max Planck Institute of Macrostructure Physics (Halle) and Post-doctoral studies from the same Institute. He has been a permanent staff member at the Faculty of Engineering, CAU of Kiel in 2009-2011. Presently, he is a group leader of the group “Structure Determination and Electron Microscopy” at the Leibniz Institute of Surface Modification (IOM). He was awarded Otto Hahn Medal from the Max Planck Society in 2008. He has authored and co-authored more than 50 scientific publications in peer reviewed journals and about the same number of conference papers.

Email: andriy.lotnyk@iom-leipzig.de