Optical and electronic properties of N/B doped graphene

Since its discovery in 2004, the graphene has attracted great attention because of its unique chemical bonding structure, which has excellent chemical, thermal, mechanical, electrical and optical properties. Due to the graphene being a zero band gap material, it has a limited development in the field of nano electronics. Therefore, in order to broaden its application scope, it is very important to carry out a study on opening the band gap of graphene. In this paper, we construct three models, i.e., the intrinsic graphene model, the N-doped graphene model, and the B-doped graphene model. We study the energy band structures and the electronic densities of states for the intrinsic graphene and the N/B doped graphenes with different doping concentrations. Furthermore, we study their optical and electronic properties including the absorption spectra, the reflection spectra, the refractive indexes, the conductivities, and the dielectric functions. The results are as follows. 1) The electronic states in the vicinity of the Fermi level for the intrinsic graphene are mainly generated by the C-2p orbits, while the electronic states in the vicinity of the Fermi level for the N/B doped graphenes are mainly generated through the hybridization between C-2p and N-2p/B-2p orbits. N doped graphene is of n-type doping, while B doped graphene is of p-type doping. 2) Compared with that of the intrinsic graphene, the Fermi level of N doped graphene moves up 5 eV. In the meantime, the band gap is opened, and the Dirac cone disappears. On the contrary, the Fermi level of B doped graphene moves down 3 eV compared with that of the intrinsic graphene. However, like the N doping, the band gap is also opened, and the Dirac cone disappears. Furthermore, the N doping is more effective than the B doping in opening the energy gap of the graphene for the same N/B doping concentration. 3) The N/B doping can cause the optical and electronic properties of the graphene to change, and exert great influences on the absorption spectrum, reflection spectrum, the refractive index, and the dielectric function, however it has little influence on the conductivity. When the energy of the incident wave is larger than a certain value, the optical and electrical properties of the intrinsic graphene remain unchanged. Besides, for the above case, the corresponding energies for the N/B doped graphenes are smaller than that for the intrinsic graphene. In addition, the energy for the B doped graphene is smallest. The conclusions of this paper can provide a theoretical basis for the application of graphene in optoelectronic devices.