Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: 2D Materials I: Growth and Properties of Transition Metal Dichalcogenides, Phase Transitions

O 35.3: Vortrag

Dienstag, 2. April 2019, 14:30–14:45, H14

Phonon dispersion of bulk MoS₂ determined by high resolution electron energy loss spectroscopy — •Holger Schwarz, Christian Heidrich, Florian Speck, and Thomas Seyller — Institut für Physik, TU Chemnitz, Reichenhainer Str. 70, D-09126 Chemnitz, Germany

Transition metal dichalcogenides are currently receiving considerable interest because they are considered as potential building blocks for novel device architectures made up from 2D materials. Basic properties like, e.g. electronic structure as well as phonon and plasmon dispersion, are of fundamental interest in this respect. High resolution electron energy loss spectroscopy (HREELS) is a powerful tool for the investigation of the phononic structure of a solid. Here we use HREELS to study the phonon dispersion of molybdenum disulfide (MoS₂). A clean surface of a MoS₂ bulk crystal was prepared by mechanical cleavage and mild annealing in ultra-high vacuum (UHV). Using low-energy electron diffraction (LEED), the sample was aligned in the high symmetry directions Γ-K and Γ-M, respectively, and subsequent HREELS measurements have been performed in off-specular geometry with a fixed incident electron energy and angle by varying the detector angle of the spectrometer. The spectra were fitted using Voigt-profiles for each resolvable phonon mode. The results are in good agreement with recent DFT-calculations from literature [1] but certain differences in comparison to an earlier HREELS study [2] were noted. [1] A. Molina-Sánchez and L. Wirtz, Phys. Rev. B 84, 155413 (2011) [2] P. A. Bertrand, Phys. Rev. B 44, 5745 (1991)