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Tuning the electronic properties of metal surfaces and graphene by molecular patterning

PhD ceremony:Mr J. Li
When:January 08, 2018
Start:11:00
Supervisors:prof. dr. M.A. (Meike) Stöhr, prof. dr. P. (Petra) Rudolf
Where:Academy building RUG
Faculty:Science and Engineering

We studied the molecular self-assemblies formed by the 1,3,5-benzenetribenzoic acid and para-hexaphenyl-dicarbonitrile molecules on graphene and metal surfaces by using scanning tunneling microscopy, scanning tunneling spectroscopy, low-energy electron diffraction and angle-resolved photoemission spectroscopy measurements. Due to leaky confinement inherently present for molecular porous networks, the confined surface states can couple, resulting in the formation of new band structure as observed in angle-resolved photoemission spectroscopy measurements.

According to theoretical considerations, the electronic properties of graphene can be changed when an external periodic potential is applied onto it. In this sense, the molecular patterning method holds the promise of tuning the electronic properties of graphene due to the periodic potential induced by it.

Therefore, it is beneficial to first study the molecular self-assembly formed on graphene. The different adsorption behavior of 1,3,5-benzenetribenzoic acid molecules on Cu(111) and graphene/Cu(111) showed that graphene effectively decoupled the adsorbed molecules from the underlying metal substrate. By co-adsorption of para-hexaphenyl-dicarbonitrile molecules and Cu atoms, 2D metal-organic coordination networks stabilized by metal-ligand interactions were synthesized on graphene/Ir(111). Our results show that the molecular patterning method enables the construction of well- and long-range-ordered 2D molecular arrangements on graphene whose potential for tailoring the electronic properties of metal surfaces and graphene can now be investigated in a next step.