Temperature-Dependent Transport in Suspended Graphene

The resistivity of ultraclean suspended graphene is strongly temperature (T) dependent for 5<T<240  K. At T∼5  K transport is near-ballistic in a device of ∼2  μm dimension and a mobility ∼170 000  cm²/V s. At large carrier density, n>0.5×10¹¹  cm^-2, the resistivity increases with increasing T and is linear above 50 K, suggesting carrier scattering from acoustic phonons. At T=240  K the mobility is ∼120 000  cm²/V s, higher than in any known semiconductor. At the charge neutral point we observe a nonuniversal conductivity that decreases with decreasing T, consistent with a density inhomogeneity <10⁸  cm^-2.