Doping of graphene adsorbed on the a-SiO2 surface
Abstract
We have performed an ab initio theoretical investigation of graphene sheet adsorbed on amorphous SiO2 surface (G/a-SiO2). We find that graphene adsorbs on the a-SiO2 surface through van der Waals interactions. The inhomogeneous topology of the a-SiO2 clean surface promotes a total charge density displacement on the adsorbed graphene sheet, giving rise to electron-rich as well as hole-rich regions on the graphene. Such anisotropic distribution of the charge density may contribute to the reduction of the electronic mobility in G/a-SiO2 systems. Furthermore, the adsorbed graphene sheet exhibits a net total charge density gain. In this case, the graphene sheet becomes n-type doped, however, with no formation of chemical bonds at the graphene--SiO2 interface. The electronic charge transfer from a-SiO2 to the graphene sheet occurs upon the formation of a partially occupied level lying above the Dirac point. We find that such partially occupied level comes from the three-fold coordinated oxygen atoms in the a-SiO2 substrate.
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