First-principles Study On The Structure And Electronic Properties Of New Transition Metal Sulfides

Since the successful stripping of graphene in 2004,two-dimensional materials have quickly become a hot topic of research.Compared with three-dimensional materials,the most fascinating thing about 2D materials is that it has an ultra-high specific surface area,making it extremely sensitive to external disturbances.Therefore,the full surface properties of two-dimensional materials make it available in some specific devices.With the deepening of research on two-dimensional materials,TMD have also successfully entered the historical arena.TMD is a large system with both layered and non-layered structures that cover the entire range of electronic structures,from insulators to metals,and exhibit interesting properties.These characteristics make TMD extremely valuable in the field of optoelectronic devices such as field effect transistors,photodetectors,nanoelectronics,and nanophotonics.In addition,the discovery of new materials with targeted properties has been a hot topic in scientific research,and new physicochemical properties that may be unknown may occur.For example,adjusting the chemical composition of a material to form a new structure may make its physicochemical properties better,which has been successfully achieved in bulk materials.Another example is the formation of new materials with different sulfur contents by a series of methods.Exploring and researching new TMDs has a major impact on the future application of 2D materials.This paper focuses on two new types of TMD.?1?Z-axis strain regulates the electronic structure of single-layer MoS₂,MoSe₂and MoSSe.Using the first-principles calculation method,we systematically investigated the effects of strain on the electronic structures of single-layer MoS₂,MoSe2 and MoSSe.The study shows that under the Z-axis stress,the single-layer MoS2,MoSe₂ and MoSSe band structures will undergo major changes.It is found that the bandgap almost linearly decrease with the increase of the axial?both compressive strain and tensile strain?.More attractively,a semiconductor-metal transition is predicted for MoS₂,MoSe₂ and MoSSe under axial strain.Although the physical mechanism of the different modes of strain on the band gap regulation is slightly different,the essential reason is that the stress causes the redistribution of the nanofilm.Our calculation results indicate that the applied stress is one of the effective ways to control the bandgap of single-layer MoS₂,MoSe₂ and MoSSe.The bandgap is continuously adjustable under the action of stress,which can construct the controllable nano-equipment and broaden the application of TMD.?2?A new TMD with a molybdenum to sulfur ratio of 2:3 is predicted.Based on the first-principles and in combination with experiments,we predicted a new TMD Mo₂S₃ with a molybdenum-sulfur ratio of 2:3.Through calculation,we prove that Mo₂S₃ can exist stably from the perspective of phonon spectrum and formation energy.And through the HAADF simulation control,it is proved that the structure we predicted is highly unified with the experimental structure.In addition to this,the electronic properties of this new material are also calculated.Our computational structure shows that Mo₂S₃ is a direct bandgap semiconductor with a bandgap of 0.429 eV,and its carrier mobility is highly anisotropic.The discovery and research of Mo₂S₃ provides more possibilities for the application of TMD in various fields in the future.