DFT simulation of interfacial interaction of graphene/SiO2 composites

Thoroughly understanding the graphene/SiO2 interfacial properties is of great significance for improving the performance of graphene-based nanoelectronic devices. In this work, the first-principle density functional theory (DFT) method was applied to systematically investigate the interfacial interaction and electronic properties of graphene on the beta-cristobalite SiO2 surface. It was first demonstrated that the Si-terminated beta-cristobalite SiO2 substrate has a strong chemical covalent interaction with the pristine graphene, whereas the hydroxylated SiO2 surface just shows weak vdW interaction with graphene. The interlayer water molecules between graphene and SiO2 can reduce the adhesion energy for the graphene/SiO2 composites, in which the water layers provide the main contribution to the graphene adhesion with the water-coated SiO2. The effects of the SiO2 surface polarity and the interfacial water geometry on the electronic properties of graphene were investigated. The electron transfer between hydroxylated SiO2 and graphene is highly related to the surface silanol density. Meanwhile, the interlayer water molecules could induce a minor electron transfer from graphene to the surfaces, resulting in the hole-doping of graphene. Our simulation provides a new understanding of the interaction for graphene/SiO2 interfaces.