Abstract
Graphene exhibits rich new physics and great promise for applications in electronics. The half-integer quantum Hall effect and high carrier mobility are critically dependent on interactions with impurities/substrates and localization of Dirac fermions in realistic devices. We microscopically study these interactions using scanning tunnelling spectroscopy (STS) of exfoliated graphene on a SiO2 substrate in an applied magnetic field. The magnetic field strongly affects the electronic behaviour of the graphene; the states condense into well-defined Landau levels with a dramatic change in the character of localization. In zero magnetic field, weakly localized states are created by the substrate induced disorder potential. In strong magnetic fields, the two-dimensional electron gas breaks into a network of interacting quantum dots formed at the potential hills and valleys of the disorder potential. Our results demonstrate how graphene properties are perturbed by the disorder potential; a finding essential for the physics and applications of graphene.
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Acknowledgements
We would like to acknowledge M. Stiles and S. Adam for fruitful discussions and S. Blankenship, A. Band, and F. Hess for their technical assistance. We thank D. Davidovic and C. E. Malec for informing us of their unpublished work on tunnelling in graphene.
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The graphene sample was fabricated by S.J. and N.N.K. STM/STS measurements were carried out by S.J., G.M.R., N.N.K. and J.A.S. The data analysis and preparation of the manuscript were carried by S.J., G.M.R., J.A.S., D.B.N. and N.B.Z. The Raman spectroscopy measurements to confirm single-layer graphene flakes were carried by I.C. and A.R.H-W.
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Jung, S., Rutter, G., Klimov, N. et al. Evolution of microscopic localization in graphene in a magnetic field from scattering resonances to quantum dots. Nature Phys 7, 245–251 (2011). https://doi.org/10.1038/nphys1866
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DOI: https://doi.org/10.1038/nphys1866
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