Leiden University Scholarly Publications

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Jong, T.A. de (2022)

Superlattices in van der Waals materials: a low-energy electron microscopy study

Doctoral Thesis
In this PhD thesis, the recombination of different atomic lattices in stacked 2D materials such as twisted bilayer graphene is studied. Using the different possibilities of Low-Energy Electron Microscopy (LEEM), the domain forming between the two atomic layers with small differences is studied. Superlattices in three such 2D material systems are studied. In twisted bilayer graphene, the small difference is caused by a twist of approximately one degree between the layers. In graphene on SiC, the difference is caused by the lattice mismatch between a buffer layer bound to the substrate and the next graphene layer. For both, we show that domains of different shapes and sizes occur and relate them to strain and lattice mismatch. The third system studied is tantalum disulfide. In this layered material, two different superlattices occur: a superlattice between atomic layers with different atomic arrangements in the layers, so-called polytypes, and the...Show moreIn this PhD thesis, the recombination of different atomic lattices in stacked 2D materials such as twisted bilayer graphene is studied. Using the different possibilities of Low-Energy Electron Microscopy (LEEM), the domain forming between the two atomic layers with small differences is studied. Superlattices in three such 2D material systems are studied. In twisted bilayer graphene, the small difference is caused by a twist of approximately one degree between the layers. In graphene on SiC, the difference is caused by the lattice mismatch between a buffer layer bound to the substrate and the next graphene layer. For both, we show that domains of different shapes and sizes occur and relate them to strain and lattice mismatch. The third system studied is tantalum disulfide. In this layered material, two different superlattices occur: a superlattice between atomic layers with different atomic arrangements in the layers, so-called polytypes, and the superlattices between the atomic lattice and the Charge Density Waves (CDW). CDWs cause a large temperature dependent resistivity change. The influence of a mixture of different polytypes on the precise CDW states is studied using LEEM spectroscopy and local Low-Energy Electron Diffraction.Show less
Graphene
Low-Energy Electron Microscopy
Condensed matter physics
Twisted bilayer graphene
Domain boundaries
2D materials
Charge density wave
All authors
Jong, T.A. de
Supervisor
Molen, S.J. van der
Co-supervisor
Tromp, R.M.
Committee
Ropers, C.; Zandvliet, H.; Conesa-Boj, S.; Batenburg, J.; Ruitenbeek, J. van: Aarts, J.
Qualification
Doctor (dr.)
Awarding Institution
Leiden Institute of Physics (LION), Faculty of Science, Leiden University
Date
2022-11-03
Title of host publication
Casimir PhD Series
ISBN (print)
9789085935308

Publication Series

Name
2022-20

Funding

Sponsorship
This work was financed by the Dutch Research Council (NWO) as part of the Frontiers of Nanoscience programme