Local electronic properties of functionalized graphene studied with scanning tunneling microscopy and spectroscopy

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Graphene, a two-dimensional single sheet of carbon atoms arranged in a honeycomb lattice, is attracting tremendous attention due to its remarkable physical properties. Particularly, its electronic structure, in which charge carriers near the Fermi level mimic massless relativistic particles (Dirac fermions), provides a perfect base for studying questions of quantum electrodynamics with experimental techniques commonly used in materials research. Furthermore, graphene is an ideal material for future electronic devices because of its outstandingly high charge carrier mobility, mechanical stability, room-temperature ballistic transport and scalability down to nanometer size. It is therefore of crucial importance to investigate the structural and electronic properties of graphene on an atomic scale which can be done by using scanning tunneling microscopy (STM) and spectroscopy (STS).This project´s major aim is exploring the influence of functionalization on the structure and local electronic properties of graphene using STM and STS. Particular emphasis will be laid on the impact of (charged) impurities on Dirac fermions in graphene and the influence of edges and individual shapes of graphene nanoribbons (GNR), small stripes of graphene, on the electronic structure. Especially the latter is of prime interest for device applications as nanoribbons are expected to exhibit a bandgap that scales with the ribbon width and, depending on the edge configuration, spin-polarized edge states as well as local magnetism. A controlled modification of graphene´s properties will be achieved by in-situ synthesis of (functionalized) graphene using chemical vapor deposition and by employing bottom-up fabrication routines transforming organic molecules into GNRs with defined shapes and edges. The results from this project will be an important contribution to the understanding of how functionalization modifies the properties of graphene and will provide valuable input for device physics based on graphene and GNRs.