Doping And Formation Of Heterojunctions On The Electronic Structure And Photoelectric Effect Of Monolayer WS₂

The excellent properties of transition metal dichalcogenides（TMDCs）in electrical,magnetic,and optical aspects are favored by many researchers.As a member of transition metal chalcogenides,WS₂has a honeycomb structure similar to graphene,wide band gap,high electron mobility and high surface-to-volume ratio,as well as other experimental and theoretical studies.Its physical properties make it widely used in field effect transistors,optoelectronic devices,etc.,and it has become one of the more popular materials at present.Substitution doping and construction of heterojunctions are important methods to improve material properties and increase the application range of materials.Therefore,based on first-principles,this paper uses substitution doping and the construction of heterojunctions to improve the performance of monolayer 2H-WS₂.The specific research contents are as follows:（1）The phonon spectra and electronic structures of monolayer 2H-WS₂ doped with each of the four atoms,N,P,As,and Sb,were studied.First,the phonon spectra of the four atoms,N,P,As,and Sb,doped with monolayer 2H-WS₂ were calculated to show the thermodynamic stability of these four doped systems.The electronic structures before and after doping are also compared,and it can be found that the forbidden band widths of N,P,As,and Sb doped monolayer 2H-phase WS₂decrease respectively,where the N-doped system has a narrower forbidden band width and makes the N-doped WS₂ system exhibit the characteristics of a p-type semiconductor,and the three doped systems,P,As,and Sb,cause a small reduction in the forbidden band width,and the valence bands of all three doped systems cross the Fermi energy level,P,As,and Sb doped monolayer 2H phase WS₂ respectively also show the characteristics of p-type semiconductors,so N,P,As,and Sb these four atoms are p-type dopants.（2）The effects of N,P,As,Sb doped monolayer 2H-WS₂ on the photoelectric effect were studied.The results show that the substitution doping of these four kinds of atoms can effectively enhance the photoelectric effect of the monolayer 2H-WS₂,and the N system performs the best,which can obtain the largest photocurrent and the highest polarization sensitivity.In addition,we further investigated the regulation mechanism of substitution doping on the photoelectric effect of monolayer 2H-WS₂.（3）The photoelectric effect in the monolayer Mo Se₂-WS₂ transverse heterojunction was investigated.By calculating the differential charge density of Mo Se₂-WS₂ transverse heterojunctions to illustrate the stability of covalent bonding connections and calculating their energy band structures,it was found that Mo Se₂-WS₂ transverse heterojunctions exhibit the characteristics of conductors.A significant photoelectric effect can be observed in the range covering almost the whole visible light and peak photocurrents are obtained at 2.8 e V,respectively,which originates from the construction of heterojunctions reducing the spatial inversion symmetry of the material and narrowing the forbidden band width.Our results were further verified by analyzing the total density of states of the monolayer Mo Se₂-WS₂ transverse heterojunction.