Modulation Of Electronic Structure,optical And Gas Adsorption Properties Of Twin Graphene By Doping And Electric Field

Graphene has extremely high carrier mobility of high hardness,good ductility and heat conduction performance,excellent electrical and optical properties,therefore they are widely used in nano-electronics field such as sensors,new energy batteries,photosensitive devices.However,the zero band gap of graphene limits its application in semiconductor nano electronic devices.Twin graphene,an allotrope of two-dimensional semiconductor carbon with inherent band gap,shows great potential in nanoelectronics.In order to further explore the excellent properties and potential applications of twin graphene,based on first principles,we systematically studied the regulation law and microscopic mechanism of electronic structure and optical properties of twin graphene by electric field and dual doping were obtained.The research contents and results are as follows:(1)By substituting the C atoms of ortno,meta and para in 3p element X(X=Al,Si,P)and 2p element Y(Y=B,N,O),the structural stability,magnetic properties and electronic properties of the XY dual-doped system were investigated.And the influence of doping concentration on the structural stability,magnetic properties and electronic structural properties of AlB intersite double doping system.The results show that AlB,AlN,AlO,SiB,SiN,SiO,PB,PN and PO dual doped twin graphene systems are thermodynamically stable,among which AlB,SiB and PB dual doped twin graphene systems have the strongest stability,while AlO,SiO and PO double doped twin graphene systems have the weakest stability.There is a strong charge transfer between the doped atom and C atom,and the amount of charge transfer ranges from 0.172 e to 2.098 e.Generally,Al atoms,Si atoms,P atoms and B atoms lose charge,while N atoms,O atoms and C atoms gain charge,thus forming stable covalent bonds between doped atoms and C atoms,which can further improve the stability of the system.Double doping can effectively adjust the band gap of the twin graphene,and partial dual doping can transform the direct band gap of the twin graphene into indirect band gap.AlO,SiN,SiO,PB-TGmeta interposition doped twin graphene(AlO-TGmeta,SiN-TGmeta,SiO-TGmeta,PB-TGmeta)and PO ortho and para doped twin graphene(PO-TGortho,PO-TGpara)changed their original semiconductor properties to Properties of gold.In addition,when the doping concentration is 5.6%and 11.1%,the AlB-TG system exhibits high spin polarization metal characteristics.Therefore,double doping can effectively adjust the electronic characteristics and magnetic properties of twin graphene,especially the AlB dual doping system with increased doping concentration has great development potential in spintronic devices.(2)The adsorption properties of CO and NO on twin graphene doped with Pd and Ti were investigated,and the effect of electric field on the stability and electronic structural properties of the adsorption system was also investigated.The adsorption stability increases with the increase of electric field strength.NO is more sensitive than CO to adsorption by TG-TM.The adsorption of CO and NO altered the electronic structure of the TG-TM system.In particular,the adsorption of NO increased the band gap of the system,which resulted in spin splitting.This indicates that significant changes in the electronic structure properties of the system can be used to detect NO.On the other hand,the positive and negative electric fields have the same effect on the stability and magnetic moment.With the increase of electric field,the adsorption stability of CO and NO gas is also enhanced.The magnetic moment of TG-Pd-CO,TG-Pd-NO and TGTi-NO systems firstly increases and then decreases with the increase of electric field,while the magnetic moment of TG-Ti-CO system increases with the increase of electric field.Overall,our results indicate that TG-TM systems have potential applications as a sensor for the storage,removal,and detection of CO and NO gases.(3)In this section,we investigated the optical properties(absorption coefficient,reflection coefficient,refraction coefficient,energy loss coefficient,real and imaginary parts of dielectric function,etc.)of twin graphene systems,and we also explored the effects of 3d transition metal doping(Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn)on the optical properties of twin graphene.The large difference between the vertical polarization component and parallel polarization component of the dielectric function reflects the anisotropy of optical properties of the twin graphene.The introduction of 3d transition metals resulted in new absorption peaks in the infrared and visible regions of the twin graphene,especially the introduction of Fe and Cu enhanced the absorption of infrared light.Compared with the reflection coefficient of the twin graphene,the reflection coefficient of the Fe,Co,Ni,Cu,Zn doped twin graphene are significantly enhanced.In particular,the Cu and Zn doped twin graphene results in redshift of the reflection peak in the infrared region.The refraction coefficient of the transition metal doped twin graphene in the parallel polarization component is larger than that in the vertical polarization direction.The imaginary part of dielectric function of Fe,Co,Ni,Cu,Zn doped twin graphene shows some peaks in the range of 0～5.0eV,which proves that the introduction of transition metal can excited electrons from occupied state to empty state to make in-band transition.Compared with Sc,Ti,V,Cr and Mn doped twin graphene,Fe,Co,Ni,Cu and Zn doped twin graphene exhibit more excellent optical properties in terms of reflection,refraction,and absorption,so it has great development potential in infrared detection and photovoltaic materials.