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Berlin 2024 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 21: Optical Analysis of Thin Films

DS 21.5: Vortrag

Freitag, 22. März 2024, 11:00–11:15, A 053

Exploring the Tunability of Phonon Properties in Ultra-Thin Bismuth Films — •Felix Hoff1, Timo Veslin1, Abdur Rehman Jalil2, Peter Kerres2, Jonathan Frank1, Thomas Schmidt1, Yazhi Xu3, Dasol Kim1, Riccardo Mazzarello3, and Matthias Wuttig1,21I. Institute of Physics (IA), RWTH Aachen University, Germany — 2Peter Grünberg Institute - JARA-Institute Energy Efficient Information Technology (PGI-10), Germany — 3Dipartimento di Fisica, Sapienza University of Rome, Italy

In recent years, ultra-thin bismuth films have gathered attention for applications in thermoelectrics, ferroelectrics, and recently for topological applications, too. Our study focuses on the systematic exploration of ultra-thin bismuth films, utilizing advanced characterization techniques to unveil the intriguing changes in phonon properties as the layer thickness is reduced. Raman spectroscopy and optical fs pump probe spectroscopy were employed to measure phonon frequencies and lifetimes, exposing a complex interplay of factors influencing the observed hardening and softening of phonon modes. Additional investigations employ XRD, revealing structural modifications and distortions. DFT calculations unravel the intricate relationship between structural changes, chemical bonding, and optical properties. We determine the layer-thickness-dependent dielectric function, which show remarkable confinement effects. Epitaxially grown samples, detailed in a prior publication, ensure reproducibility. Motivated by achieving high-quality thin films, our work contributes to understanding the underlying mechanisms governing phonon properties in ultra-thin bismuth.

Keywords: Coherent Phonons; Bismuth; Femtosecond; Raman; Tunability

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