  We have achieved mobilities in excess of 200,000 cm^2/Vs at electron
densities of ~2*10^11 cm^-2 by suspending single layer graphene. Suspension
~150 nm above a Si/SiO_2 gate electrode and electrical contacts to the graphene
was achieved by a combination of electron beam lithography and etching. The
specimens were cleaned in situ by employing current-induced heating, directly
resulting in a significant improvement of electrical transport. Concomitant
with large mobility enhancement, the widths of the characteristic Dirac peaks
are reduced by a factor of 10 compared to traditional, non-suspended devices.
This advance should allow for accessing the intrinsic transport properties of
graphene.
