Study On Electronic Structure,Optics And Thermodynamic Properties Of Single Layer Graphene

Due to the distinct crystal structure and properties,grapheme with a two-dimensional structure had attracted more and more attention of the widely application fields.However,the characteristics of zero band gap limited the application of graphene in semiconductor devices.In this paper,the electronic properties,optical properties,thermodynamic properties and Raman spectroscopy of the substitute-doped monolayer grapheme were studied be means of the first principles calculation,which provided theories direction for the semiconductor devices,the graphene FM lasers and other applications fields.The main research content is as follows:(1)The electronic structure and optical properties of the monolayer graphene were calculated via the first-principles calculation.The results showed that the monolayer graphene possessed the zero band gap characteristics,and the intersection of the conduction band and the valence band is a Dirac point,which exhibits metallic properties.The absorption and reflection of single-layer graphene in the terahertz,infrared and visible light bands is very small,almost in a transparent state,and the absorption and reflection of light mainly occurred in the ultraviolet band.Complex refractive index exhibited birefringence characteristic.Conductivity was almost zero in the terahertz and infrared bands,however,in the ultraviolet band region the conductivity reached on the maximum value.The energy loss in the terahertz and infrared bands was zero,and in the visible light band was very small,but in the ultraviolet band obtained the maximum value.(2)The effects of the monoatomic substitution-doped on the electronic properties of monolayer graphene were investigated by using IIIA atom B and VA atom N as doping atoms.The results showed that the band gap of the graphene was opened after doping,and the metal property was converted into the semiconductor property,which had theoretical significance for the studies of graphene in the fields of semiconductor devices and photoelectric information.(3)The effects of the monoatomic substitution doped on the optical properties of monolayer graphene were investigated by selecting IIIA atom B and VA atom N as doping atoms.The results showed that the range of light absorption,reflectivity,refractive index,electrical conductivity and energy loss of grapheme decreased after B doped.The absorption rate,reflectivity,refractive index,electrical conductivity and energy loss of B-doped single layer graphene in the terahertz,infrared and visible light bands were very small,and mainly appeared in the ultraviolet light band.Compared with monolayer graphene,in the ultraviolet band,the absorbance,reflectance,refractive index,electrical conductivity,and energy loss of the B-doped single layer graphene decreased significantly.The N-doped single layer graphene changed obviously in light absorption,reflectance,refractive index,electrical conductivity,and energy loss at the terahertz,infrared,and visible light bands.Absorption,reflectance,refractive index,electrical conductivity,and energy loss intensity in the ultraviolet band were significantly lower than those of monolayer graphene.(4)The thermodynamic properties and Raman spectra of the monolayer graphene were calculated by first-principles calculations.The results showed that the Debye temperature,molar heat capacity,enthalpy and entropy of the monolayer grapheme increased with the increase of temperature,but the free energy decreased.The peaks of Raman spectrum were composed of a D peak,a G peak and a 2D peak,and the G peak was the dominant characteristic peak.