Letter abstract
Nature Physics 4, 377 - 381 (2008)
Published online: 13 April 2008 | doi:10.1038/nphys935
Subject Categories: Electronics, photonics and device physics | Condensed-matter physics | Nanotechnology
Charged-impurity scattering in graphene
J.-H. Chen1,2,3,7, C. Jang1,2,3,7, S. Adam2,3,4, M. S. Fuhrer1,2,3, E. D. Williams1,2,3,5,6 & M. Ishigami2,3,8
Since the initial demonstration of the ability to experimentally isolate a single graphene sheet1, a great deal of theoretical work has focused on explaining graphene's unusual carrier-density-dependent conductivity 
(n), and its minimum value (min) of nearly twice the quantum unit of conductance (4e2/h) (refs 1, 2, 3, 4, 5, 6). Potential explanations for such behaviour include short-range disorder7, 8, 9, 10, 'ripples' in graphene's atomic structure11, 12 and the presence of charged impurities7, 8, 13, 14, 15, 16, 17, 18. Here, we conduct a systematic study of the last of these mechanisms, by monitoring changes in electronic characteristics of initially clean graphene19 as the density of charged impurities (nimp) is increased by depositing potassium atoms onto its surface in ultrahigh vacuum. At non-zero carrier density, charged-impurity scattering produces the widely observed linear dependence1, 2, 3, 4, 5, 6 of (n). More significantly, we find that min occurs not at the carrier density that neutralizes nimp, but rather the carrier density at which the average impurity potential is zero15. As nimp increases, min initially falls to a minimum value near 4e2/h. This indicates that min in the present experimental samples1, 2, 3, 4, 5, 6 is governed not by the physics of the Dirac point singularity20, 21, but rather by carrier-density inhomogeneities induced by the potential of charged impurities6, 8, 14, 15.
- Materials Research Science and Engineering Center, University of Maryland, College Park, Maryland 20742, USA
- Physics Department, University of Maryland, College Park, Maryland 20742, USA
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742, USA
- Condensed Matter Theory Center, University of Maryland, College Park, Maryland 20742, USA
- Laboratory for Physical Sciences, University of Maryland, College Park, Maryland 20742, USA
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
- These authors contributed equally to this work
- Present address: Department of Physics, University of Central Florida, 4000 Central Florida Boulevard, Orlando, Florida 32816-2385, USA
Correspondence to: M. Ishigami2,3,8 e-mail: ishigami@physics.ucf.edu
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