Effect of charge impurities and defects on transport properties of graphene. (a) The conductivity () versus gate voltage for a pristine sample (black curve) and three different potassium doping concentrations at 20 K in UHV. Lines represent empirical fits [34]. (b) Inverse of mobility () as a function of ion dosage for different samples and irradiated ions ( and ). The dashed line corresponds to the behavior for the same concentration of potassium doping [35].
