Study On Weak Interaction And Electronic Structure Between Two-dimensional Material Stacked Structures

As a new type of low-dimensional photoelectric material,two-dimensional material has many unique physical and chemical properties.As the first two-dimensional material to enter the field of vision of researchers,graphene is considered to be widely used in low-dimensional nanoelectronic devices due to its high electron mobility,low resistivity and many other excellent physical properties.However,the zero band gap structure of graphene limits its application to a certain extent,while monolayer Mo S₂and WS₂,as transition metal sulfides,not only have the common advantages of two-dimensional materials such as high electron mobility and high specific surface area,but also have the physical characteristics of wide band gap,which is conducive to more extensive application in the field of optoelectronic devices.With the deepening of the research on two-dimensional materials,it has been found that stacking different two-dimensional materials together to form van der Waals heterojunctions can effectively break the limitations of single two-dimensional materials in application.This stacking form can combine the advantages of two or more different types of two-dimensional materials,thus improving the performance of new low-dimensional nano-optoelectronic devices.The study of weak interaction is of great significance in many fields such as low-dimensional nano-optoelectronic materials.The formation of van der Waals heterojunction is accomplished by the weak interaction between layers.However,the current research on the two-dimensional stacked structure of van der Waals heterojunction mainly focuses on electronic structure,photoelectric properties,etc.,especially the quantitative analysis of the weak interaction force between stacked two-dimensional materials is less.In this paper,bilayer graphene,Graphene/Mo S₂and Graphene/WS₂Graphene/WS₂heterojunctions as the research objects,and uses the combination of quantitative analysis and first-principles calculation to deeply analyze the weak interaction between the dominant double-layer materials.The energy decomposition analysis based on molecular force field（EDA-FF）method is used to quantitatively analyze and explore the nature of the weak interaction between two-dimensional stacked materials,and combined with a variety of weak interaction analysis methods to analyze its form of action,and further analyze the optical properties of two two-dimensional stacked heterostructures.The electronic structure of the three two-dimensional material stacked heterostructures is calculated later.Then,by applying electric fields of different directions and sizes,the change of the average charge differential density before and after the formation of the two-dimensional stacked material reflects the change of the weak interaction between the layers,and then clarifies the influence of the change of the weak interaction between the two-dimensional stacked structures on the electronic structure.The main research contents of this paper are as follows:（1）The optimization of three two-dimensional stacking structures of bilayer graphene,Graphene/Mo S₂and Graphene/WS₂was completed in Gaussian 16software.The weak interaction analysis of the three stacking structures was carried out by combining wave function analysis software Multiwfn and molecular visualization program VMD.Firstly,the region of van der Waals interaction between three kinds of two stacked structures is shown.After that,three two-dimensional stacking structures are analyzed by EDA-FF.The calculation results show that the dispersion effect is the main effect of the two-dimensional stacking structure.The sources and modes of several weak interactions were further explored by electrostatic potential analysis,differential charge density analysis and delocalized electron analysis.In addition,the optical absorption spectra and electron circular dichroism（ECD）of Graphene/Mo S₂and Graphene/WS₂heterostructures are calculated.The results are helpful to understand the optical properties of two-dimensional stacked heterostructures and effectively promote the continuous progress of optoelectronic applications of two-dimensional structural devices.（2）The structural optimization and electronic structure calculation of monolayer graphene、Mo S₂、WS₂,AA and AB stacked bilayer graphene,Graphene/Mo S₂,Graphene/WS₂heterojunction were completed in Materials Studio 2021 Castep.The band structure and density of states of three single-layer materials and three heterojunctions are obtained.The band characteristics of the three materials in the single-layer case and after the formation of the heterojunction are summarized.Through the analysis of the total density of states and the partial density of states of each atom,the contribution of each atom to the total density of states at the Fermi level is obtained.（3）Using AA stacked graphene,Graphene/Mo S₂and Graphene/WS₂heterojunctions optimized in Castep,by applying a gradually increasing electric field in both positive and negative directions to the three stacked structures,the influence of the weak interaction strength between the two-dimensional stacked structures on the electronic structure is summarized.It is concluded that the stronger the weak interaction,the smaller the band gap in the electronic structure,and vice versa.