Invited Paper NM+MS+NS+NC-WeM9
Intrinsic and Extrinsic Limits of Charge Carrier Mobility in Graphene

Wednesday, October 22, 2008, 10:40 am, Room 309

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. Due to the high conductivity and charge carrier mobility, graphene is being considered for a number of applications ranging from transparent, conducting thin films to high-speed electronics. Here I will discuss experiments performed on atomically-clean graphene on SiO₂¹ 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 graphene³ limits the room-temperature mobility to 200,000 cm²/Vs at a carrier density of 10¹² cm^-2, higher than any known material. However, conduction in current graphene samples is limited almost entirely by extrinsic scattering due to charged impurities in the substrate² and substrate polar optical phonons³ currently, pointing out the importance of substrate engineering for improving graphene devices.⁴ I will discuss the implications for the future of graphene technologies in terms of the manufacturing methods for large-area graphene currently being explored, such as solution processing methods, chemical vapor deposition, and epitaxial growth on metals and insulators.

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, Nature Physics 4, 377 (2008).
³ “Intrinsic and Extrinsic Performance Limits of Graphene Devices on SiO₂,” J. H. Chen, C. Jang, S. Xiao, M. Ishigami, M. S. Fuhrer, Nature Nanotechnology 3, 206 (2008).
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).