TY - THES
AU - Sforzini, Jessica
TI - The influence of the substrate on the structure and electronic properties of carbon-based 2D materials
PB - RWTH Aachen University
VL - Dissertation
CY - Aachen
M1 - RWTH-2017-05554
SP - 1 Online-Ressource (XIII, 145 Seiten) : Illustrationen, Diagramme
PY - 2017
N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1 - Dissertation, RWTh Aachen University, 2017
AB - The exploration of two-dimensional materials, such as graphene, has become the hottest research of interest in recent years. In this dissertation, we examine two classes of materials considered of importance for both fundamentals studies and devices applications, namely graphene on 6H-SiC(0001) and palladium-/platinum- phthalocyanine on Ag(111), with the aim of assessing the interactions at the interface. Using different surface science techniques, we are able to study the modification of their electronic and structural properties in relation to the supporting substrate. At first, we present a new approach used to gauge the strength of the interactions at the interface in graphene/substrate systems which is based on the determination of the adsorption height of the graphene layer. From the comparison of different graphene/SiC interfaces, i.e., carbon buffer layer, hydrogen intercalation and germanium intercalation, we find that the graphene layer is best decoupled from the underlying substrate when the hydrogen intercalation is present at the interface. The effect of the supporting substrate (and interface) on the graphene properties is further investigated upon doping. We find that depending on the type of interface, i.e., carbon buffer layer or hydrogen intercalation, the quantity as well as the variety of nitrogen dopants substituted into the graphene lattice varies but not the n-type carrier increase. This leads to the conclusion that the effective doping of graphene depends on the supporting material. In fact for hydrogen intercalated graphene, the nitrogen dopants partially replace hydrogen at the intercalation, contributing to the doping ('proximity doping') but leading to an increment of the interaction at the interface. In contrast, the carbon buffer layer is found inert against the nitrogen doping, but active against the boron doping; a behavior most likely dependent on the preparation method. Finally, the molecular symmetry reduction (from the D<sub>4h</sub> symmetry group) via degeneracy lifting of the platinum- and palladium-phthalocyanine/Ag(111) complexes is investigated using vibrational spectroscopy. Because of the presence of an interfacial dynamical charge transfer, some vibrational peaks show a Fano-type line shape. Their assignment to vibrational modes which are infrared active only in the C<sub>2v</sub> symmetry group proves that a preferential charge transfer from the Ag surface into one of the originally doubly degenerate lowest unoccupied molecular orbitals takes place, i.e. the electronic degeneracy is lifted and the molecule-surface complex acquires the twofold symmetry.
LB - PUB:(DE-HGF)11
DO - DOI:10.18154/RWTH-2017-05554
UR - https://publications.rwth-aachen.de/record/691010
ER -
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