Excitons in epitaxially grown WS2 on Graphene: a nanometer-resolved EELS and DFT study
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2024
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| author | Bergmann, Max Belz, Jürgen Maßmeyer, Oliver Dogahe, Badrosadat Ojaghi Günkel, Robin Glowatzki, Johannes Beyer, Andreas Solovev, Ivan Drawer, Jens-Christian Esmann, Martin Pasko, Sergej Krotkus, Simonas Heuken, Michael Wippermann, Stefan Volz, Kerstin |
| author_facet | Bergmann, Max Belz, Jürgen Maßmeyer, Oliver Dogahe, Badrosadat Ojaghi Günkel, Robin Glowatzki, Johannes Beyer, Andreas Solovev, Ivan Drawer, Jens-Christian Esmann, Martin Pasko, Sergej Krotkus, Simonas Heuken, Michael Wippermann, Stefan Volz, Kerstin |
| contents | In this study, we investigate excitonic properties of epitaxially grown WS2, which is of particular interest for various applications due to its potential for upscaling to wafer sized structures. Understanding the effect of the dielectric environment due to changing layer numbers and multi-material heterostructures on the optical properties is crucial for tailoring device properties. Monochromated electron energy loss spectroscopy in a scanning transmission electron microscope is employed to characterize the excitonic spectrum of WS2 on graphene grown by metal organic chemical vapor deposition. This technique provides the required spatial resolution at the nanometer scale in combination with high quality spectra. To complement the experimental results, theoretical investigations using density functional theory and applying the Bethe-Salpeter equations are conducted. We find that by transitioning from mono- to bi- to multilayers of WS2 the spectra show redshifts for both, the K-valley excitons at about 2.0 and 2.4 eV as well as excitonic features of higher energies. The latter features originate from so called band nesting of transitions between the Gamma- and K-point. In summary, this study provides valuable insights into the excitonic properties of WS2 in different layer configurations and environments, which are realistically needed for future device fabrication and property tuning. Finally, we can show that nanometer scale electron spectroscopy supported by careful theoretical modelling can successfully link atomic structure and optical properties, such as exciton shifts, in non-idealized complex material systems like multilayer 2D heterostructures. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_13020 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Excitons in epitaxially grown WS2 on Graphene: a nanometer-resolved EELS and DFT study Bergmann, Max Belz, Jürgen Maßmeyer, Oliver Dogahe, Badrosadat Ojaghi Günkel, Robin Glowatzki, Johannes Beyer, Andreas Solovev, Ivan Drawer, Jens-Christian Esmann, Martin Pasko, Sergej Krotkus, Simonas Heuken, Michael Wippermann, Stefan Volz, Kerstin Materials Science In this study, we investigate excitonic properties of epitaxially grown WS2, which is of particular interest for various applications due to its potential for upscaling to wafer sized structures. Understanding the effect of the dielectric environment due to changing layer numbers and multi-material heterostructures on the optical properties is crucial for tailoring device properties. Monochromated electron energy loss spectroscopy in a scanning transmission electron microscope is employed to characterize the excitonic spectrum of WS2 on graphene grown by metal organic chemical vapor deposition. This technique provides the required spatial resolution at the nanometer scale in combination with high quality spectra. To complement the experimental results, theoretical investigations using density functional theory and applying the Bethe-Salpeter equations are conducted. We find that by transitioning from mono- to bi- to multilayers of WS2 the spectra show redshifts for both, the K-valley excitons at about 2.0 and 2.4 eV as well as excitonic features of higher energies. The latter features originate from so called band nesting of transitions between the Gamma- and K-point. In summary, this study provides valuable insights into the excitonic properties of WS2 in different layer configurations and environments, which are realistically needed for future device fabrication and property tuning. Finally, we can show that nanometer scale electron spectroscopy supported by careful theoretical modelling can successfully link atomic structure and optical properties, such as exciton shifts, in non-idealized complex material systems like multilayer 2D heterostructures. |
| title | Excitons in epitaxially grown WS2 on Graphene: a nanometer-resolved EELS and DFT study |
| topic | Materials Science |
| url | https://arxiv.org/abs/2402.13020 |