Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 29: Poster: 2D Materials
O 29.17: Poster
Dienstag, 19. März 2024, 12:30–14:30, Poster A
Exploring Excitonic Dispersions in 2D WS2 through Spatially Resolved Electron Energy Loss Spectroscopy — •Max Bergmann, Jürgen Belz, Oliver Maßmeyer, Badrosadat Ojaghi Dogahe, Robin Günkel, Johannes Glowatzki, Andreas Beyer, Stefan Wippermann, and Kerstin Volz — Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany
Two-dimensional transition metal dichalcogenides have attracted considerable attention in materials science, particularly in the field of valleytronics, due to their unique indirect-to-direct bandgap transition and enhanced quantum efficiency in the monolayer limit. In this study we use a monochromated scanning transmission electron microscope to measure the electron energy loss spectrum of WS2 providing nanometer-scale spatial resolution. The measurements reveal redshifts of the excitonic excitations due to a change in the WS2 layer number for both the excitons residing at the K-point of the band structure and excitonic features stemming from more diverse excitations at points between Γ and K. To assess the origin of these excitations, theoretical investigations, namely density functional theory with Bethe-Salpeter equations on top, were used. This comprehensive investigation provides valuable insights into the excitonic properties of WS2 across different layer configurations, highlighting in particular the dispersion of excitons with respect to changes in layer number.
Keywords: excitons; 2D; EELS; WS2; bilayer