Ab initio calculations of the electronic properties and the transport phenomena in graphene materials

The density functional theory (DFT) is used to study the electronic properties and the energy structure of monolayers of graphene supercells consisting of 18 and 54 carbon atoms and doped with Ge and Si atoms.The properties of graphene supercells are studied in the framework of the generalized gradient approximation (GGA). The Ge-doped graphene supercells with carbon atom vacancies are found to demonstrate the antiferromagnetic spin ordering; the local magnetic moments formed in carbon atoms are estimated. The density of states (DOS) and the supercell band structure are approximated. The Ge-doping of graphene in comparison with Si-doping is shown to noticeably open an energy gap in graphene. The physical regularities of the charge transfer are studied with the allowance for the temperature dependence of the electrical conductivity of a hydrogenated graphene (HGG). It is shown that, at temperatures 4–125 K, the HGG conductivity corresponds to the hopping mechanism of charge transfer with a variable jump distance. The density of localized states near the Fermi level, the jump distances, and the energy spread of the trap states near the Fermi level are determined. The concentration of localized states in the HGG energy gap is estimated.