Atmospheric chemical doping can be used to modify the electronic properties of graphene. Although extensive experimental work on tuning atmospheric chemical doping of graphene has been reported, such a study of graphene on SiC is still lacking. Here we report that the chemical doping (oxygen and water vapor) of low-carrier-density monolayer epitaxial graphene on SiC can be readily tuned by a simple low-temperature (T near 450 K), in-situ vacuum annealing method. Such an approach allows, for the first time, the observation of a crossover from disordered graphene (mu-sub-t/mu-sub-q ~2) to an ordinary metal (mu-sub-t/mu-sub-q ~1) with decreasing carrier density where mu-sub-t and mu-sub-q are transport mobility and quantum mobility, respectively. In the low carrier density limit, our results are consistent with the theoretical prediction that mu-sub-t is inversely proportional to charged impurity density. Our data also suggests that atmospheric chemical doping can be used to vary intervalley scattering in graphene which plays a crucial role in backward scattering events.
Pub Type: Journals
carrier density, graphene, chemical doping, quantum mobility, electron scattering