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arXiv · 0708.2408

Charged Impurity Scattering in Graphene

J. H. Chen·C. Jang·M. S. Fuhrer·E. D. Williams·M. Ishigami
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Abstract

Since the experimental realization of graphene1, extensive theoretical work has focused on short-range disorder2-5, ''ripples''6, 7, or charged impurities2, 3, 8-13 to explain the conductivity as a function of carrier density sigma_(n)[1,14-18], and its minimum value sigma_min near twice the conductance quantum 4e2/h[14, 15, 19, 20]. Here we vary the density of charged impurities nimp on clean graphene21 by deposition of potassium in ultra high vacuum. At non-zero carrier density, charged impurity scattering produces the ubiquitously observed1, 14-18 linear sigma_(n) with the theoretically-predicted magnitude. The predicted asymmetry11 for attractive vs. repulsive scattering of Dirac fermions is observed. Sigma_min occurs not at the carrier density which neutralizes nimp, but rather the carrier density at which the average impurity potential is zero10. Sigma_min decreases initially with nimp, reaching a minimum near 4e2/h at non-zero nimp, indicating that Sigma_min in present experimental samples does not probe Dirac-point physics14, 15, 19, 20 but rather carrier density inhomogeneity due to the impurity potential3, 9, 10.

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J. H. Chen, C. Jang, M. S. Fuhrer, E. D. Williams, M. Ishigami. 2007-11-09. Charged Impurity Scattering in Graphene. https://doi.org/10.1038/nphys935

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