Journal
NANO LETTERS
Volume 13, Issue 8, Pages 3576-3580Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl4012529
Keywords
Graphene; noncontact atomic force microscopy; Kelvin probe force microscopy; charged impurity scattering; charge inhomogeneity
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Funding
- University of Maryland NSF-MRSEC [DMR 05-20471]
- U.S. ONR MURI program
- National Research Foundation Singapore [NRF-NRFF2012-01]
- Grants-in-Aid for Scientific Research [23310096, 24651148] Funding Source: KAKEN
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Kelvin probe microscopy in ultrahigh vacuum is used to image the local electrostatic potential fluctuations above hexagonal boron nitride (h-BN) and SiO2, common substrates for graphene. Results are compared to a model of randomly distributed charges in a two-dimensional (2D) plane. For SiO2, the results are well modeled by 2D charge densities ranging from 0.24 to 2.7 X 10(11) cm(-2), while h-BN displays potential fluctuations 1-2 orders of magnitude lower than SiO2, consistent with the improvement in charge carrier mobility for graphene on h-BN compared to SiO2. Electron beam exposure of SiO2 increases the charge density fluctuations, creating long-lived metastable charge populations of similar to 2 x 10(11) cm(-2) at room temperature, which can be reversed by heating.
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