Atomic Structure of Graphene on SiO2

Abstract

We employ scanning probe microscopy to reveal atomic structures and nanoscale morphology of graphene-based electronic devices (i.e., a graphene sheet supported by an insulating silicon dioxide substrate) for the first time. Atomic resolution scanning tunneling microscopy images reveal the presence of a strong spatially dependent perturbation, which breaks the hexagonal lattice symmetry of the graphitic lattice. Structural corrugations of the graphene sheet partially conform to the underlying silicon oxide substrate. These effects are obscured or modified on graphene devices processed with normal lithographic methods, as they are covered with a layer of photoresist residue. We enable our experiments by a novel cleaning process to produce atomically clean graphene sheets. Graphene,1,2 a single layer of graphite, is an unique material with exotic electronic properties.1-8 A hexagonal two-dimensional network of carbon atoms composes graphene; it is exactly one atom in thickness, and every carbon atom is a surface atom. Therefore, substrate-induced structural distortion,9 adsorbates,7 local charge disorder,10 atomic structure at the edges,4,11 and even atomic scale defects12 could be very important for transport properties of graphene.