title: Free-standing graphene at atomic resolution.
abstract: Research interest in graphene, a two-dimensional crystal consisting of a single atomic plane of carbon atoms, has been driven by its extraordinary properties, including charge carriers that mimic ultra-relativistic elementary particles. Moreover, graphene exhibits ballistic electron transport on the submicrometre scale, even at room temperature, which has allowed the demonstration of graphene-based field-effect transistors and the observation of a room-temperature quantum Hall effect. Here we confirm the presence of free-standing, single-layer graphene with directly interpretable atomic-resolution imaging combined with the spatially resolved study of both the pi --> pi* transition and the pi + sigma plasmon. We also present atomic-scale observations of the morphology of free-standing graphene and explore the role of microstructural peculiarities that affect the stability of the sheets. We also follow the evolution and interaction of point defects and suggest a mechanism by which they form ring defects.
authors.affiliation: SuperSTEM, STFC Daresbury Laboratory, Warrington WA4 4AD, UK. m.h.gass@liv.ac.uk
authors.forename: Mhairi H
authors.initials: MH
authors.lastname: Gass
authors.forename: Ursel
authors.initials: U
authors.lastname: Bangert
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Bleloch
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Rahul R
authors.initials: RR
authors.lastname: Nair
authors.forename: A K
authors.initials: AK
authors.lastname: Geim
mesh_terms: D002244:Carbon / Q000737:chemistry; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods; D004583:Electrons; D004735:Energy Transfer; D008422:Materials Testing / Q000379:methods*; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D011789:Quantum Theory; D046590:Spectroscopy, Electron Energy-Loss; D013816:Thermodynamics
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D002244:Carbon