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| Home > Publications database > Growth and Excitation Dynamics of Epitaxial 2D Materials and Molecular Layers Studied by Electron and Momentum Microscopy |
| Book/Dissertation / PhD Thesis | FZJ-2026-02457 |
2026
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-892-6
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-02457
Abstract: The properties of modern nanomaterials are governed by their atomic structure, as well as by electronic interactions at their surfaces and internal interfaces. The present thesis is situated within this contemporary field of research and focuses on the synthesis and analysis of two model systems of functional surface structures. The first project is located in the field of twistronics and studies the growth of unconventionally oriented graphene layers on silicon carbide (SiC). The second project focuses on probing the transiently occupied orbitals of surface-adsorbed organic molecules in time and space. The first project aims for a better understanding of an already established growth process for the production of unconventionally oriented monolayer graphene on SiC, which offers a promising route to produce 30 ◦ -twisted bilayer graphene. The growth process involves two preparation steps, namely, the chemical vapor deposition of a BN layer and its replacement by graphene upon annealing at increasingly high temperatures. The mechanism that determines the orientation of the graphene layer is of particular interest, as well as the influence of the preparation parameters on the composition and quality of the BN layer, and therefore also the quality of the resulting graphene. These aspects were investigated by employing low-energy electron microscopy (LEEM), a powerful technique to probe the crystalline structure and domain configuration of surfaces, and to investigate growth processesin situ and in real time. It is demonstrated that the BN layer’s composition and quality – and thus the quality of the resulting unconventionally oriented graphene – depend sensitively on the heating rate during BN synthesis. In the second project, photoemission orbital tomography (POT) was combined with time-resolved photoelectron spectroscopy to image transiently occupied orbitals of surface-adsorbed organic molecules on ultrafast timescales for the first time. A monolayer of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecules on oxygen-passivated Cu(001) serves as the sample. The oxide layer decouples the molecules from the substrate, enabling observation of ultrafast excitation dynamics. Using time-resolved POT (tr-POT), the population of the lowest unoccupied molecular orbital (LUMO) after optical excitation was visualized in a time- and momentum-resolved manner. Overall, this work demonstrates that precise control over the growth of layered nanomaterials contributes to a better understanding of complex growth mechanisms and can facilitate the development of new characterization techniques.
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