关键词: 石墨烯, 掺杂, 单轴应变, 第一性原理计算, 电子结构, 磁性

Doped graphene has been widely focused because of its modifications on properties of graphene. Syntheses of doped graphene have been hotspots for years and experimentalists are still struggling for obtaining controllable high-quality doped graphene. Usually, rigorous experimental conditions are required. In order to make it easier to dope impurities into graphene, we proposed that uniaxial strain can reduce the formation energy of the process of doping graphene. By using first-principles calculations, we first calculated the formation energy of doping graphene with boron, nitrogen, aluminum, silicon and phosphorus under different uniaxial strains (from -6% to 6%). After that, we studied the effect of uniaxial strain on the electronic structure and magnetism of doped graphene. The DFT calculations were carried out within the framework of plane-wave density functional theory, implemented in the Vienna ab initio simulation package (VASP). The projector-augmented-wave potentials were employed to describe the electron-ion interaction and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) was used for exchange-correlation functional. The kinetic energy cutoff of 400 eV was adopted for the plane-wave expansion and the Brillouin zone was sampled by the Monkhorst-Pack scheme. Periodic boundary conditions were used in the simulations, and the graphene sheet was modeled by a rectangular supercell with 60 carbon atoms, indicating that the dosage concentration is 1.67%. We found that uniaxial strain can apparently change the formation energy of doping processes: tensile and compressive strain can reduce the formation energy of graphene doped with boron and nitrogen, respectively, while the formation energy of graphene doped with aluminum, silicon and phosphorus can be reduced by both tensile and compressive strain. The band gaps of doped graphene range from ca. 0.1 to 0.9 eV and can be changed by the uniaxial strain, which will reach a maximum under 3% tensile strain for all the dopant species. Boron-, nitrogen-, aluminum- and silicon-doped graphene are nonmagnetic. On the contrary, phosphorus-doped graphene is magnetic and its magnetic moment decreases under both tensile and compressive strain.

Key words: graphene, doping, uniaxial strain, first-principles calculations, electronic structure, magnetism