AVS 56th International Symposium & Exhibition
    Graphene Topical Conference Monday Sessions
       Session GR-MoM

Paper GR-MoM8
Is Fullerene-Intercalation in Graphite a Vehicle to Graphene Surface Layer Doping?

Monday, November 9, 2009, 10:40 am, Room C3

Session: Graphene and 2D Carbon Nanostructures
Presenter: P. Reinke, University of Virginia
Authors: P. Reinke, University of Virginia
S. O'Donnell, University of Virginia
Correspondent: Click to Email
In order to exploit the extraordinary properties of graphene several materials-based challenges have to be addressed to reach full device functionality. The challenges include opening and control of a bandgap, n- and p type doping while preserving the ambipolarity at the K-point, and sustaining the high mobility of charge carriers. We introduce here a novel a novel and highly versatile method for the modulation of the electronic properties of graphene, which is based on fullerene (C60)-graphite intercalation compounds (C60-GIC). The goal is to electronically decouple the top graphene sheet from its substrate through the introduction of an intercalated layer of fullerene molecules, which are a wide bandgap material and thus do not significantly perturb the bandstructure around the Dirac point of graphene. The fullerene layer can subsequently be doped and thus the charge transfer to the graphene is controlled via the modulation of the intercalated fullerene layer. The synthesis of the C60-GICs is achieved by an annealing process, where the supersaturation of the gasphase with fullerenes is used to drive the molecule into the graphite lattice. The parameter space for successful intercalation is controlled by the substrate temperature, fullerene concentration and the defect structure of the graphite. The intercalation process is observed with scanning tunneling microscopy and spectroscopy which is probes the geometric and electronic structure of the top layer. The presence of sub-surface fullerenes is detected through the appearance of a Moire pattern and a weak distortion of the topography, usually presented in a well-defined area around step edges. The spatial distribution of intercalated regions is used to describe the kinetics of the intercalation process and to elucidate the mechanistic aspects of the material synthesis. The graphene doping through the incorporation of a second dopant (e.g. K) in the C60 layer is investigated with STM. The electronic structure of the top graphene layer is measured with STS, and the spatial distribution of charge-puddles and their relation to the sub-surface C60 lattice will be discussed.