| AVS 56th International Symposium & Exhibition | |
| Graphene Topical Conference | Tuesday Sessions |
| Session GR+EM+MS-TuM |
| Session: | Graphene and Carbon-based Electronics |
| Presenter: | Q.H. Wang, Northwestern University |
| Authors: | Q.H. Wang, Northwestern University M.C. Hersam, Northwestern University |
| Correspondent: | Click to Email |
Graphene has attracted significant attention due to its unique electronic structure, high carrier mobilities, and quantum relativistic phenomena. Epitaxial graphene grown on SiC(0001) is a promising material for next-generation technology because it allows for wafer-scale processing. In order to realize its full potential for a diverse range of devices, the bare graphene sheet must be incorporated with other materials via chemical functionalization schemes. Recent progress reported in the literature include the demonstration of atomic layer deposition of Al2O3 on mechanically exfoliated graphene sheets functionalized by carboxylate-terminated perylene derivatives,1 and the formation of monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) at cryogenic temperatures on epitaxial graphene.2 In this study, we report the room-temperature formation of self-assembled monolayers of PTCDA on epitaxial graphene.3 We characterize the molecular ordering and electronic properties of these monolayers using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). The molecules self-assemble into stable, well-ordered monolayers that are arranged in a herringbone phase with extended domains spanning hundreds of nanometers. At submonolayer coverage, PTCDA forms stable, isolated molecular islands. The molecular ordering is unperturbed by either defects in the epitaxial graphene or atomic steps in the underlying SiC surface. Scanning tunneling spectroscopy (STS) performed on the PTCDA monolayers reveals strong features in the electronic density of states that are distinct from the pristine graphene regions. The demonstration of robust, uniform organic functionalization of epitaxial graphene presents opportunities for exploring self-assembly chemistry on graphene, tailoring the chemical functionality of graphene, and templated growth and deposition of other materials as potential routes toward realizing graphene-based molecular electronic and sensing devices.
1. X.R. Wang, S.M. Tabakman, and H.J. Dai, J. Am. Chem. Soc. 130, 8152-8153 (2008).
2. P. Lauffer, K.V. Emtsev, R. Graupner, T. Seyller, and L. Ley, Phys. Status Solidi B, 245, 2064-2067 (2008).
3. Q.H. Wang and M.C. Hersam, Nature Chemistry, in press (2009).