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Atomic-scale transport in epitaxial graphene


The high carrier mobility of graphene1,2,3,4 is key to its applications,and understanding the factors that limit mobility is essential for future devices. Yet, despite significant progress, mobilities in excess of the 2×105 cm2 V−1 s−1 demonstrated in free-standing graphene films5,6 have not been duplicated in conventional graphene devices fabricated on substrates. Understanding the origins of this degradation is perhaps the main challenge facing graphene device research. Experiments that probe carrier scattering in devices are often indirect7, relying on the predictions of a specific model for scattering, such as random charged impurities in the substrate8,9,10. Here, we describe model-independent, atomic-scale transport measurements that show that scattering at two key defects—surface steps and changes in layer thickness—seriously degrades transport in epitaxial graphene films on SiC. These measurements demonstrate the strong impact of atomic-scale substrate features on graphene performance.

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Figure 1: LEEM, STM and macroscale potential measurement of graphene on SiC.
Figure 2: Scanning tunnelling potentiometry of terraces and monolayer–bilayer junctions.
Figure 3: Single-layer graphene overlaying substrate steps.
Figure 4: Details of current flow around steps.


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We thank A. Ellis and M. C. Reuter of IBM for their assistance with experimental aspects of this work, and R. Möller and X. Chen for discussions.

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Authors and Affiliations



S-H.J. carried out scanning tunnelling potentiometry experiments, J.B.H. and R.M.T. grew the graphene and carried out LEEM; J.T. and V.P. carried out the calculations; S-H.J., F.M.R., J.B.H. and R.M.T. collaborated on equipment and experimental design; all authors wrote the paper.

Corresponding authors

Correspondence to Shuai-Hua Ji or F. M. Ross.

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The authors declare no competing financial interests.

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Ji, SH., Hannon, J., Tromp, R. et al. Atomic-scale transport in epitaxial graphene. Nature Mater 11, 114–119 (2012).

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