Chemical gating of epitaxial graphene through ultrathin oxide layers

We achieve a controllable chemical gating of epitaxial graphene grown on metal substrates by exploiting the electrostatic polarization of ultrathin SiO2 layers synthesized below it. Intercalated oxygen diffusing through the SiO2 layer modifies the metal-oxide work function hole doping graphene. The graphene|oxide|metal heterostructure behaves as a gated plane capacitor with the in-situ grown SiO2 layer acting as a homogeneous dielectric spacer, whose high capacity allows the Fermi level of graphene to be shifted by a few hundreds meV when the oxygen coverage at the metal substrate is of the order of 0.5 monolayer. The hole doping can be finely tuned by controlling the amount of the interfacial oxygen, as well as by adjusting the thickness of the oxide layer. After complete thermal desorption of oxygen the intrinsic doping of SiO2 supported graphene is evaluated in the absence of contaminants and adventitious adsorbates. The demonstration that the charge state of graphene can be changed by chemically modifying the buried oxide/metal interface hints at the possibility of tuning level and sign of doping by the use of other intercalants capable to diffuse through the ultrathin porous dielectric and reach the interface with the metal.s are then performed to address the impact of such results on electron cloud predictions in the LHC.