First-principles Study On Electrical Properties Of Graphene And Phosphene Heterojunction

The successful preparation of graphene has attracted wide attention for two-dimensional(2D)materials.Subsequently,many new 2D materials were prepared.As an important 2D materials,phosphorene not only has excellent physical and chemical properties similar to graphene,but also makes up for the defect of graphene's zero band gap,making it an ideal candidate material for the fabrication of electronic devices such as field effect transistors and semiconductor sensors.Phospholene has the characteristics of in-plane covalent bonds and out-of-plane van der Waals interactions,and can be combined with different 2D materials to form different van der Waals heterostructures.These heterostructures have significant effects in improving electronic properties,and have become the focus of research in recent years.Therefore,in this paper,we explore the geometric structure,electronic and optical properties of graphene,phosphorene and their heterostructure by using first-principles caculation based on density functional theory.Firstly.the structure stability,electronic and magnetic propertics were investigated for non-metal(B,N)and metal(Na,Mn)atoms edge-modified zigzag graphens nanoribbons(ZGNR)with different widths.Furthermore,we also studied the electronic structures propertis of edge-decorated ZGNR systems by applied vertical electric fields with different intensities.All systems of the non-metal atoms(B,N)and metal atoms(Na,Mn)edge-decorated ZGNR with different widths can form stable structures.With the increasing intensity of electric fields perpendicular to the nanoribbon surface,the stability is almost unchanged for the most stable[N-ZG]4 system,and the stability is increases for the[Mn-ZG]4 system but decreases for the[B-ZG]4 and[Na-ZG]4 systems.The electric field promotes the further transfer of charge from atoms(B,Na,Mn)to the C atoms of graphene in[M-ZG]system,and hinders the transfer of charge from C atom to N atom in[N-ZG]system.The magnetisms are decrease gradually for the[N-ZG]and[Na-ZG]systems while increase gradually for[B-ZG]and[Mn-ZG]systems.The results show that the structure stability,electronic and magnatic properties can be regulated effectively by the electric fields with different intensities for the atoms edge-decorated ZGNR systems,which can provide a theoretical basis for the application of graphene nanoribbons in the field of nanoeletronics.Secondly,the geometric structure and electronic properties of bilayer phosphorene nanoribbons(BPNRs)with different widths(N=4-10)have been studied,and we further intercalated the 3d transition metal adatoms(TM=Sc,Ti,V,Cr,Mn,Fe,Co,Ni,and Cu)into the centre of the four-atom wide BPNR(4-BPNR).We find that the atomic stacking of the BPNRs reorders from the AA to the AE stacking.The AE-stacked structure is the most stable structure for one-dimensional zigzag BPNRs.All the BPNRs with widths N=4-10 exhibit semiconductor character with indirect band gaps(1.17,1.01,0.92,0.84,0.75,0.74,and 0.72 eV),which gradually decrease with increasing nanoribbon width.The calculated bond lengths,charge transfer,and difference charge density of[PMnP]systems indicate that there are strong chemical interactions between the TM atoms and their adjacent P atoms in the BPNRs,resulting in the formation of TM-P ionic bonds.The adsorption of TM atoms induces various electronic structures in 4-BPNR.The[PTMP]i systems exhibit metallic properties with the adsorption of Sc,Co,and Cu atoms,and semiconductor properties with the adsorption of Ti,V,Cr,Mn,Fe,and Ni atoms with band gaps of 0.30,0.18,0.19,0.20,0.61,and 0.08 eV,respectively.The Ni and Cu adsorption systems show magnetic quenching with no magnetic moments in all the compound systems[PTMP].Our results show that TM atom-adsorbed bilayer phosphorene nanoribbons exhibit tunable electronic structures and magnetic properties for potential applications in nanoelectronics.Finally,we investigated the electronic structures and optical properties of graphene/phosphorene(G/P)heterostructures and their response to external electric fields.The results reveal that vertically stacked monolayer graphene and phosphorene can form heterostructures through weak van der Waals interactions,and that an external electric field can effectively control the band structure of the G/P heterostructure.The dielectric functions of G/P heterostructures are those of a metal and semiconductor in the parallel and vertical polarization directions,respectively,which indicate significant anisotropic optical properties of the G/P heterostructure.Various optical parameters such as dielectric functions,absorption coefficient,reflectivity,refractive index,and energy loss spectrum have different effects according to the direction and intensity of the external electric field.Under an external electric field,the spectrum peaks shift to the lower-energy zone for the dielectric functions and optical absorption coefficients of the G/P heterostructure.The parallel polarization components of the reflection spectrum shift to a lower-energy state in the range of 8.9-15.2 eV under the electric field,but the vertical polarization components of the reflection spectrum are blue-shifted with increasing intensity of a negative electric field,while the peak increases rapidly under a positive electric field.The electric field influences the refractive index in the far infrared region,with the static refractive index being enhanced under the electric field intensities of 0.8,-0.4 and-0.6 V/A.The introduction of an external electric field enhances the energy loss of light in the ultraviolet waveband(approximately 16.3 eV)but suppresses the energy loss spectrum at approximately 9.8 eV.This research provides a useful theoretical basis for the potential application of G/P heterostructures in nanoelectronics-and optoelectronics-based devices.