Electric Field Effect in Planar Single-Layer Graphene

We describe free-standing single-layer crystals of graphene, which are one carbon atom thick but extend over many microns laterally. This two-dimensional fullerene macromolecule is obtained by mechanical exfoliation and allows standard microfabrication procedures, as described in our earlier paper in Science \textbf{306}, 666 (2004). We have found graphene to be stable under ambient conditions, conductive and of remarkably high quality. Using graphene films, we have fabricated transistor-like devices and studied their properties from room to liquid-helium temperatures. Graphene exhibits a strong ambipolar electric-field effect with room-temperature mobilities of electrons and holes up to $\approx $10,000 cm$^{2}$/Vs, which implies ballistic transport over submicron distances. At low temperatures, we have observed pronounced Shubnikov-de Haas oscillations and well-developed plateau-like features, indicating onset of the quantum Hall effect. Graphene is found to be a zero-gap 2D semiconductor. Analysis of the quantum oscillations also indicates the linear, Dirac-like spectrum of its carriers.