Dresden 2020 – scientific programme

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DS: Fachverband Dünne Schichten

DS 12: Thermoelectric and Phase Change Materials

DS 12.1: Talk

Monday, March 16, 2020, 16:30–16:45, CHE 91

Atom Probe Investigation of Intermixing and Thermal stability in GeTe-Sb₂Te₃ Superlattices for Memory Applications — •Nikita Polin, Oana Cojocaru-Mirédin, Henning Hollerman, Alexander Meledin, and Matthias Wuttig — I. Physikalisches Institut (IA), RWTH Aachen University, Aachen, Germany

A chalcogenide superlattice is a periodic structure of layers of two (or more) chalcogenide materials with typical layer thickness of several nanometers. Devices based on GeTe-Sb₂Te₃-superlattices were found to switch with one order of magnitude lower power consumption compared to conventional bulk based Ge₂Sb₂Te₅ devices. However, the layers were found to be prone to intermix during deposition at elevated temperatures. Investigation of the thermal stability of the superlattices is thus of applicational and scientific interest.

For this purpose sputtered and annealed GeTe-Sb₂Te₃-superlattices are studied by Atom Probe Tomography (APT), Transmission Electron Microscopy and X-Ray-Diffraction in a correlative manner. Due to the 3D chemical information of the specimens arising from the APT some unexpected findings on the nanoscale could be made: Besides the conventional defects as grain boundaries more exotic nanostructural defects, such as layer splitting, layer dissolving and layer gluing, were found. Additionally heterointerfaces between Ge-rich phases and the surrounding Ge₂Sb₂Te₅ were found even at high annealing temperatures of 350^∘C. Such interfaces might be decisive for the electrical, magnetic, thermoelectric and optical properties of the superlattices.