Electronic structure of graphene and doping effect on SiO2

First-principles calculations show that the electronic structure of graphene on SiO2 strongly depends on the surface polarity and interface geometry. Surface dangling bonds mediate the coupling to graphene and can induce hole or electron doping via charge transfer even in the absence of extrinsic impurities in substrate. In an interface geometry where graphene is weakly bonded to an O-polar surface, graphene is p doped, whereas n doping takes place on a Si-polar surface with active dangling bonds. We suggest that electron and hole doping domains observed on SiO2 are related to different surface polarities.