SKM 2023 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 15: Optical Analysis of Thin Films II
DS 15.4: Vortrag
Donnerstag, 30. März 2023, 12:15–12:30, SCH A 316
Temperature Dependence of Coherent Phonon Oscillations in Metavalently Bonded Solids — •Timo Veslin1, Felix Hoff1, Julian Mertens1, Jonathan Frank1, and Matthias Wuttig1,2,3 — 1I. Institute of Physics (IA), RWTH Aachen University — 2Jülich-Aachen Research Alliance (JARA FIT and JARA HPC) — 3PGI 10 (Green IT), Forschungszentrum Jülich GmbH
Femtosecond optical pump probe measurements are carried out in order to detect changes in the reflectivity of the material response of MBE grown metavalently bonded (MVB) materials on sub-ps timescales. MVB differs significantly from metallic, ionic and covalent bonding. Examination of reflectivity changes due to the coherent phonon response provides insight into the ultrafast lattice dynamics and relaxation of MVB materials. To this end, the mechanism of displacive excitation of coherent phonons (DECP) is used to analyse the highly symmetric A1 modes. The material response consists of the ultrafast carrier excitation and a slower carrier relaxation together with a damped harmonic phonon oscillation measured in the transient reflectivity trace. The temperature dependence of the frequency, lifetime and oscillation amplitude of the coherent phonon A1 mode in Sb2Te3, GeTe and Bismuth will be presented. This allows to identify phonon coupling effects and dephasing mechanisms, as well as the temperature dependence of phonon frequencies. Furthermore, the results are supported by optical and structural data recorded at room temperature. These measurements will help to better understand the MVB mechanism which governs phase change materials.