DFT study on electronic and optical properties of graphene modified by phosphorus

Abstract

The photoelectric properties of graphene are modulated by replacing carbon atoms with phosphorus atoms. The studies have revealed that the band gap of graphene is opened after adding phosphorus atoms and the Dirac cone disappears. The Fermi level goes into the conduction band, which behavior is similar to n-type doping. The band gaps of phosphorus-doped graphene are 0.166 eV, 0.32 eV, 0.811 eV, 0.86 eV and 1.262 eV, respectively, and the corresponding phosphorus doping concentration are 3.125%, 6.25%, 9.375%, 12.5% and 15.625% successively. For phosphorus-doped graphene, phosphorus atom gains electrons while carbon atom loses electrons. The loss of electrons for carbon atoms mainly come from C-p orbitals, a few contributions come from C-s orbitals. The effective widths of the absorption spectra of the phosphorus-doped graphene are narrower than that of the pristine graphene, and the peak value is reduced, too. Interestingly, when the doping concentration is lower than 9.375%, the reflectivity of pristine graphene is higher than that of phosphorus-doped graphene. When the concentration of phosphorus are 9.375%, 12.5% and 15.625%, electrons are prone to inelastic collisions with incident electrons. The results of the study provide a theoretical basis for the future application of graphene in optical and optoelectronic devices.