| Two-dimensional materials are considered as a new direction of future semiconductor materials research due to their excellent electronic properties.Spintronics has always been a hot topic in the research and exploration of two-dimensional materials.To realize spintronic devices,the key problem lies in the manipulation and injection of electron spin.Rashba spin-orbit coupling effect provides an effective way for spin manipulation by electric field.Spin injection can be realized in spin-polarized materials.In this paper,Rashba spin splitting and spin polarization in III-VI two-dimensional materials are studied based on first-principle calculations under density functional theory.The main contents are as follows:1.we predict a new type of two-dimensional material with inversion asymmetry-InXF(X=S,Se,Te).The thermodynamic and dynamic stabilities of these materials are verified by the calculation of cohesive energies and phonon spectra.The electronic structures show that these materials not only have direct band gaps,but also have Rashba spin splitting band characteristics at conduction band bottom.We select InTeF monolayer with the largest Rashba parameter as an example to further study the mechanisms of spin splitting.The results show that the strong spin-orbit coupling effect is caused by the overlap of the orbitals of In and Te atoms and the strong intralayer polar electric field leads to the strong Rashba effect in the InTeF monolayer.In addition,we analyze the influences of strains on the Rashba effect of InTeF monolayer.It is found that applying biaxial strains has little impact on the bonding nature of In-F bonds,which is responsible for the polarized electric field required by Rashba effect.Therefore,the Rashba spin splitting of InTeF monolayer does not change much when strains or substrate materials are introduced,which indicates that the material is suitable for constructing two-dimensional structures for spintronic devices.Our work provides a theoretical basis for exploring the applications of two-dimensional Rashba materials and related devices.2.The effect of carrier doping on electron spin polarization in armchair β-InSe nanoribbons has been systematically studied.Like two-dimensional β-InSe,the spin polarization and half-metal state in armchair β-InSe nanoribbons with H atoms modified can be induced by hole doping.However,for armchair β-InSe nanoribbons without H atoms modification,both electron and hole doping can lead to spin polarization,and the nanoribbon will also transform into half-metal state at a certain doped hole concentration.In addition,the spin direction through the Fermi surface is reversed in the case of hole and electron doping.Compared with the case of H atom modification,the edge state of the armchair β-InSe nanoribbon without modification dominates the spin polarization,and the carrier aggregation on the edge atom also promotes the spin polarization of the edge state. |
