Effect of sample preparation on charged impurities in graphene substrates

ORAL

Abstract

The mobility of graphene as fabricated on SiO$_{2}$ has been found to vary widely depending on sample preparation conditions. Additionally, graphene mobility on SiO$_{2}$ appears to be limited to $\sim$20,000 cm$^{2}$/Vs, likely due to charged impurities in the substrate. Here we present a study of the effect of fabrication procedures on substrate charged impurity density (n$_{imp}$) utilizing ultrahigh-vacuum Kelvin probe force microscopy. We conclude that even minimal SEM exposure, as from e-beam lithography, induces an increased impurity density, while heating reduces the number of charges for sample substrates which already exhibit a higher impurity density. We measure both SiO$_{2}$ and h-BN and find that all n$_{imp}$ values observed for SiO$_{2}$ are higher than those observed for h-BN; this is consistent with the observed improvement in mobility for graphene devices fabricated on h-BN over those fabricated on SiO$_{2}$ substrates.

*This work was supported by the US ONR MURI program, and the University of Maryland NSF-MRSEC under Grant No. DMR 05-20471.

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Authors

  • K.M. Burson

    • Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742-4111, USA

  • C.R. Dean

    • Columbia University, New York, New York, 10027, USA

  • K. Watanabe

    • Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan

  • T. Taniguchi

    • Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan

  • J. Hone

    • Columbia University, New York, New York, 10027, USA

  • P. Kim

    • Columbia University, New York, New York, 10027, USA

  • W.G. Cullen

    • Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742-4111, USA

  • Michael Fuhrer

    • Department of Physics, University of Maryland
    • University of Maryland
    • CNAM-UMD
    • Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742-4111, USA
    • Center for Nanophysics and Advanced Materials University of Maryland, College Park
    • Center for Nanophysics and Advanced Materials, University of Maryland, College Park