Molecular self-assembly on graphene has attracted increasing attention over the past few years due to its potential for applications ranging from organic electronics over photovoltaics to spintronics. On the one hand, the chemical inertness and the low density of states near the Fermi level make graphene a perfect choice as a buffer layer to decouple adsorbed molecules from the underlying (metallic) substrate. Importantly, this holds the promise to preserve the intrinsic properties of the adsorbed species such as magnetic or catalytic properties. On the other hand, molecular self-assembly on graphene can be also employed as a promising method for tuning the electronic properties of graphene (doping or band gap opening) on a macroscopic scale while for this purpose, the molecule graphene interaction has to be larger than a mere physisorptive one. In my presentation I will discuss the structural and electronic properties for two molecule-graphene systems. For the first system, 1,3,5-benzenetribenzoic acid on graphene/Cu(111), different coverage dependent assemblies were observed. [1] We could demonstrate that the underlying Cu(111) surface influences the structural arrangement of the molecules. With respect to the electronic properties, angle-resolved photoemission spectroscopy measurements showed n-doping of graphene. For the second system, parahexaphenyl-dicarbonitrile (NC-Ph6-CN) on graphene, we observed the arrangement of a close-packed structure independent of coverage. However, a non-negligible influence of graphene on this arrangement with a peculiar shift of every 4th molecule was detected, which was not observed for the case of metallic substrates or for the bulk phase. Adding Cu adatoms to submonolayer coverage of NC-Ph6-CN resulted in the formation of metal-organic coordination networks with varying arrangements in dependence of the stoichiometry between molecules and Cu atoms. With scanning tunneling spectroscopy we characterized the electronic properties and could identify differences between the different assembly structures. [2]

H-bonded and metal-organic coordination networks on graphene

2019 Spring National Meeting

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