The Electronic Properties of Graphene Adsorbed on the (111) HfO2 Surface – A First Principles Study

Using density functional theory calculations, we have investigated the electronic properties of graphene monolayer adsorbed on the HfO2 substrate. Our main research interest here is to explore the reason why the HfO2 substrate can significantly degrade the transport properties of the adsorbed graphene layer as revealed in the recent experiments. Our calculated results show that graphene monolayer is bounded to the HfO2 surface via the van der Waals interaction with a binding energy of around 25∼40% larger than that on a SiO2 substrate. The band gap opening at the Dirac point was found to be comparable to that on a silanol SiO2 surface, but the induced charge accumulation at the graphene/HfO2 interface is at least one order of magnitude larger than that between graphene and the silanol SiO2 surface. Moreover, when graphene monolayer was placed on top of the substrate containing an O vacancy, the adsorbed graphene layer becomes n-type doped primarily due to the charge transfer from the O vacancy site in the HfO2 substrate. Our results further show that the strong interaction between surface O vacancy and the graphene layer not only can result in a relatively larger band gap opening at the Dirac point but also can degrade the linear band dispersion in the band structure of monolayer graphene.