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DS: Fachverband Dünne Schichten

DS 15: Thermoelectric and Phase Change Materials

DS 15.2: Talk

Thursday, March 21, 2024, 10:45–11:00, A 060

Atomic-scale characterization of Cu-Te phases prepared using focused ion beam and thermal heating — •Nils Braun¹, Vladimir Roddatis², Sonja Cremer¹, Hagen Bryja¹, Lennart Voß³, Lorenz Kienle³, and Andriy Lotnyk¹ — ¹Leibniz Institute of Surface Engineering e.V. (IOM) — ²GFZ German Research Centre for Geosciences — ³Institute for Materials Science, Faculty of Engineering, University of Kiel

Cu-Te phases are interesting for thermoelectric applications. However, their crystal structure is still under debate. In this work, we prepared different nanoscale Cu-Te phases from the Cu - Sb₂Te₃ system using FIB and thermal treatment. Epitaxial or polycrystalline Sb₂Te₃ thin films are grown on p-type Si (111) and SiO₂ coated wafers, respectively, by pulsed laser deposition. A standard cross-section FIB preparation method is employed and the lamellae are investigated using advanced TEM methods and XRD.

The formation of van der Waals bonded Cu-Te phases consisting of bi- and tri-layers of Te is observed in epitaxial and polycrystalline samples. The lattice parameters and position of Cu and Te atoms in the resulting phases are determined from atomic-resolution STEM and HREELS images. The crystal structure of the bilayered phase was identified as trigonal Cu₇Te₄ and orthorhombic/tetragonal Cu₃-xTe₂. Moreover, crystal defects such as dislocations were observed in the thin films.

We acknowledge P. Hertel and A. Mill for their support and financial support by the German Research Foundation (DFG 448667535).

Keywords: Copper telluride; Thermoelectric materials; TEM; FIB