Surface Science Studies of Graphene Film and Nanoislands

Abstract

The electrical and optical properties of graphene are sensitive functions of its environment and its lateral dimension. Single, bilayer and multilayer graphene, as well as nano-sized graphene were investigated using High Resolution Electron Energy Loss Spectroscopy (HREELS) and Scanning Tunneling Microscopy. The work described in chapter 3-4 focuses on the HREELS studies of phonon and surface plasmon behaviors of epitaxial graphene on SiC(0001) with different thickness. We demonstrate that HREELS can be used as a sensitive and effective tool to determine the layer thickness of graphene. In chapter 5, we have developed a unified one-pot electrochemistry method to prepare fluorescent carbon nanoribbons, nanoparticles and graphene sheets from the exfoliation graphite electrode. In the last part, for the first time we report the synthesis of regular sized graphene nanostructures using C60 molecules and tuning its bandgap by edge functionalization using scanning tunneling microcopy and spectroscopy. We show here that Ru-catalyzed cage-opening of fullerene provides a facile route to the controllable synthesis of graphene quantum dots (GQDs). The strong C60¿Ru interaction induces the formation of surface vacancy and molecular embedding of C60 on the Ru substrate. The fragmentation of the embedded C60 at elevated temperatures produces carbon clusters which undergo diffusion and aggregation to form GQDs. The equilibrium shape of GQDs can be tailored by optimizing the annealing temperature and density of carbon clusters. In addition, we also demonstrate an in-plane donor-acceptor interaction that can open a tunable bandgap of graphene up to 0.6 eV via edge-decoration by electron-deficient C60 molecules.