Intrinsic and Extrinsic Limits of Charge Carrier Mobility in Graphene
 
Michael S. Fuhrer

Department of Physics and Center for Nanophysics and Advanced Materials, University 
of Maryland at College Park, College Park, Maryland

Graphene, a single atom-thick sheet of graphite, is a zero-gap semiconductor with an 
unusual linear dispersion relation (analogous to the Dirac equation for massless 
relativistic particles) and a density of states that vanishes at a singular point.  Graphene is 
an exciting new condensed matter system, both for the opportunity to observe the physics 
associated with massless Dirac Fermions in the laboratory, and because of materials 
parameters which make it attractive for technological applications.  However, in the few 
years since the experimental realization of graphene, progress toward cleaner (higher 
mobility) samples has largely stalled.  I will discuss experiments performed on 
atomically-clean graphene on SiO2[1] in ultra-high vacuum to determine the intrinsic and 
extrinsic limits of mobility in graphene[2,3], which point out both the promise of the 
material as well as the technological challenges that lie ahead in realizing better graphene 
samples.  Intrinsic scattering by the acoustic phonons of graphene[3] limits the room-
temperature mobility to 2 x 105 cm2/Vs at a carrier density of 1012 cm-2, higher than any 
known material.  However, extrinsic scattering due to charged impurities in the 
substrate[2] and substrate polar optical phonons[3] currently impose much more severe 
limits on the mobility, pointing out the importance of substrate engineering for improving 
graphene devices[4].

[1] "Atomic Structure of Graphene on SiO2," Masa Ishigami, J. H. Chen, W. G. Cullen, 
M. S. Fuhrer, and E. D. Williams, Nano Letters 7, 1643 (2007).
[2] "Charged Impurity Scattering in Graphene," J. H. Chen, C. Jang, M. S. Fuhrer, E. D. 
Williams, and M. Ishigami, arXiv:0708.2408.
[3] "Intrinsic and Extrinsic Performance Limits of Graphene Devices on SiO2," J. H. 
Chen, C. Jang, S. Xiao, M. Ishigami, M. S. Fuhrer, arXiv:0711.3646.
[4] "Printed Graphene Circuits," Jian-Hao Chen, Masa Ishigami, Chaun Jang, Daniel R. 
Hines, Michael S. Fuhrer, and Ellen D. Williams, Advanced Materials 19, 3623 (2007).