Quality assessment of graphene: Continuity, uniformity, and accuracy of mobility measurements

David M.A. Mackenzie, Jonas D. Buron, Patrick R. Whelan, José M. Caridad, Martin Bjergfelt, Birong Luo, Abhay Shivayogimath, Anne L. Smitshuysen, Joachim D. Thomsen, Timothy J. Booth, Lene Gammelgaard, Johanna Zultak, Bjarke S. Jessen, Peter Bøggild, Dirch H. Petersen

    Research output: Contribution to journalArticlepeer-review

    Abstract

    © 2017 Tsinghua University Press and Springer-Verlag GmbH Germany With the increasing availability of large-area graphene, the ability to rapidly and accurately assess the quality of the electrical properties has become critically important. For practical applications, spatial variability in carrier density and carrier mobility must be controlled and minimized. We present a simple framework for assessing the quality and homogeneity of large-area graphene devices. The field effect in both exfoliated graphene devices encapsulated in hexagonal boron nitride and chemical vapor-deposited (CVD) devices was measured in dual current–voltage configurations and used to derive a single, gate-dependent effective shape factor, β, for each device. β is a sensitive indicator of spatial homogeneity that can be obtained from samples of arbitrary shape. All 50 devices investigated in this study show a variation (up to tenfold) in β as a function of the gate bias. Finite element simulations suggest that spatial doping inhomogeneity, rather than mobility inhomogeneity, is the primary cause of the gate dependence of β, and that measurable variations of β can be caused by doping variations as small as 10 10 cm −2 . Our results suggest that local variations in the position of the Dirac point alter the current flow and thus the effective sample shape as a function of the gate bias. We also found that such variations lead to systematic errors in carrier mobility calculations, which can be revealed by inspecting the corresponding β factor.[Figure not available: see fulltext.]
    Original languageEnglish
    Pages (from-to)3596-3605
    Number of pages10
    JournalNano Research
    Volume10
    Issue number10
    Early online date4 Apr 2017
    DOIs
    Publication statusPublished - 1 Oct 2017

    Keywords

    • CVD graphene
    • Raman mapping
    • doping inhomogeneity
    • electrical measurements
    • finite element simulations
    • hBN-encapsulated graphene
    • van der Pauw

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