Probing charge scattering mechanisms in suspended graphene by varying its dielectric environment

Graphene with high carrier mobility mu is required both for graphene-based electronic devices and for the investigation of the fundamental properties of Dirac fermions. An attractive approach to increase the mobility is to place graphene in an environment with high static dielectric constant kappa that would screen the electric field due to the charged impurities present near graphene's surface. Here we investigate the effect of the dielectric environment of graphene and study electrical transport in multi-terminal graphene devices suspended in liquids with kappa ranging from 1.9 to 33. For non-polar liquids (kappa<5), we observe a rapid increase of mu(kappa), with room-temperature mobility reaching similar to 60,000 cm(2)Vs(-1) for devices in anisole (kappa=4.3). We associate this trend with dielectric screening of charged impurities adsorbed on graphene. We observe much lower mobility mu similar to 20,000 cm(2)Vs(-1) for devices in polar liquids (kappa >= 18) and explain it by additional scattering caused by ions present in such liquids.