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DS: Fachverband Dünne Schichten

DS 9: Optical Analysis of Thin Films II

DS 9.5: Vortrag

Donnerstag, 20. März 2025, 11:15–11:30, H3

Tailoring Properties of Epitaxially Grown Bismuth Telluride Thin Films through Stoichiometric Control — •Felix Hoff, Christoph Ringkamp, Alexander Kiehn, Thomas Schmidt, Dasol Kim, Jonathan Frank, Timo Veslin, and Matthias Wuttig — I. Institute of Physics (IA), RWTH Aachen University, Germany

The Earth's crust contains a significant number of minerals formed by elements such as Bi and Te, which is surprising given their scarcity. This rich mineral diversity can be attributed to strong interlayer interactions within layered chalcogenides, leading to complex phase diagrams. Bismuth tellurides, in particular, exhibit various stacking sequences that influence their properties as thermoelectrics and topological insulators. While their structural and thermoelectric properties are well-studied in bulk forms, high-quality thin films and their optical and vibrational properties remain underexplored. We address this gap by examining the vibrational and dielectric properties of epitaxially grown thin films of nine distinct BiTe compositions grown on Si (111). Using Raman and fs pump-probe spectroscopy, we characterized the lattice dynamics while optical spectroscopy was employed to determine the dielectric properties. The variation in phonon frequencies with respect to the Bi share can be attributed to the differing strengths of the interlayer bonds. The height of the dielectric absorption peak increases with increasing Bi share, accompanied by a shift in the absorption maximum to lower photon energies. Our results demonstrate the potential of the BiTe system as a versatile and tunable platform for thin film applications.

Keywords: materials design; layered chalcogenides; metavalent bonding; bismuth telluride; thin films