| Janus transition metal dichalcogenides(Janus TMDs)monolayer,as a new representative of the two-dimensional material family,have shown great potential in many important application fields due to their excellent physical properties and chemical properties,such as electricity,optics,adsorption and catalysis.They have received widespread attention from more and more researchers.In this paper,the electronic structure and adsorption properties of two-dimensional transition metal dichalcogenide Janus MXY(M=Mo,W;X=S,Se;Y=S,Se;X≠Y)monolayer were studied.Based on the first principle,the band structure and spin orbit coupling of the(SxSe1x)MSe monolayer(x equals S/(S+Se)on the surface),which is obtained by replacing S atoms with Se in the S atomic layer of Janus MSSe monolayer,are studied by using density functional theory(DFT)calculations.The research results indicate that the variation of the energy gap of(SxSe1-x)MSe monolayer with x is consistent with that of MSSe alloy monolayer.After considering spin orbit coupling,both Dresselhaus spin splitting and Rashba spin splitting were observed in the(SxSe1-x)MSe monolayer.As x increases,the degree of Dresselhaus splitting slightly decreases,and the splitting is more pronounced at the valence band maximum than the conduction band minimum.The Dresselhaus splitting strength of(SxSe1-x)WSe monolayer is always higher than that of(SxSe1-x)MoSe monolayer,indicating that the induced splitting along the energy direction increases with the increase of M atomic number.The Rashba splitting strength of(SxSe1-x)MSe monolayer varies with x,demonstrating the feasibility of controlling the spin orbit coupling strength by changing surface components.The main reason is that compared to the traditional mirror symmetry MX2(X=S,Se),the mirror symmetry of Janus MXY along the direction perpendicular to the two-dimensional material plane is broken,resulting in a decrease in overall symmetry.The electronegativity difference between X and Y generates an inherent electric dipole and a built-in electric field,which leads to strong spin orbit coupling.It can be seen that surface component regulation of Rashba spin splitting in Janus MXY monolayer provides a new degree of freedom for spintronic applications.Meanwhile,Janus MX Y monolayer has excellent research value in the field of gas sensors due to its adjustable bandgap properties,large specific surface area,and high surface activity.In this paper,we investigated the adsorption of NO molecular on MoX2 monolayer and Janus MoSSe monolayer with and without vacancy defects by incorporating semi classical dispersion correction calculations.By comparing structural parameters and adsorption energy,etc,it was found that Janus MoSSe monolayer is more sensitive to NO molecular than MoX2 monolayer and introducing vacancies can enhance its adsorption performance for NO molecular. |
