First-principles Study Of Two-dimensional Single-layer Carbon-nitrogen Materials And Their Doping

Based on the first-principles of density functional theory,the electronic,magnetic and optical properties of the O-doped monolayer C2N and non-metallic atoms doped C3N are investigated in this paper.The effects of 1?6 oxygen doped atoms in a unit cell on the electronic,magnetic and optical properties of monolayer C2N are studied.In details,the lattice parameters,band structures,density of states,phonon dispersions,absorption and dielectric function of O-doped monolayer C2N are obtained and analyzed.The band structure indicates that monolayer C2N is a semiconductor with a direct band gap of 1.631 eV.When doped with 1,3,5 oxygen atoms,the band gaps value of the system become 0 eV.However,the band gaps of the system doped with 2 and 4 oxygen atoms decrease to 0.342 eV and 0.343 eV.It must be pointed that when the O atoms completely replaces the N atoms,the band gap of the system increases to 2.267 eV.The C2N system doped with 2,4,6 oxygen atoms is transformed from direct bandgap semiconductor to indirect bandgap semiconductor.This means that the electronic properties of the system can indeed be regulated by 1-6 oxygen atoms.The optical properties of monolayer C2N system are also affected by different number of oxygen atoms doping.However,doping nonmetal oxygen element in monolayer C2N does not affect its magnetic properties.Finally,the phonon dispersions of the O-doped system are given.There is no imaginary frequency in the six doping cases.In other words,the doping systems studied in this paper are stable.The effects of different kinds of non-metallic B,O,P,S and As substitution doping N atoms in a unit cell on the electronic.magnetic and optical properties of C3N monolayer are studied.In details,the lattice parameters,band structures,density of states,absorption and dielectric function of doped monolayer C3N are obtained and analyzed.The band structure indicates that monolayer C3N is a semiconductor with an indirect band gap of 0.409 eV.The band gaps of C3N system doped with P,O and S atoms decrease to 0 eV.The band gap of C3N system doped with B atom increases to 1.286 eV.The band gap of C3N system doped with As atom also decreases to 0.116 eV.When doped with O,P and S atoms,the pure C3N system transform from semiconductor to conductor.Therefore,doping B,O,P,S,As atoms does have effect on electronic properties.It was shown that the doping of B,O,P,S and As atoms also have effect on the optical properties of monolayer C3N systems.However,doping nonmetal B,O,P,S and As atoms in monolayer C3N does not affect its magnetic properties.