Study On Electronic Structure And Optical Properties Of Two-Dimensional Transition Metal Dichalcogenides/Graphene Heterostructure

Many properties exhibited by two-dimensional(2D)materials with atomic layer thickness provide multiple possibilities for basic research and applications.As early as 2004,graphene was successfully stripped,which sparked a wave of exploration of two-dimensional materials Graphene has been widely used in solar cells,lighting and touch screens.In recent years,two-dimensional transition metal dichalcogenides have received more and more attention.Among them,MoS2 and WSe2 were used in transparent conductive electrodes,touch screens,flexible electronic displays,and flexible field effect tubes and other fields,which show outstanding application prospects.Van der Waals heterostructure(vd WH)is one of the hottest topics in the field of physics and materials science research.One of the research goals of vdWHs is to stack two-dimensional materials with different characteristics to obtain unexpected and outstanding characteristics,achieve rich functions and novel physical effects.By building a heterostructure,the material's electronic structure,light absorption and hydrolysis capabilities will be significantly improved.vdWHs may be important materials for future optoelectronic devices and one of candidates for next-generation nanodevices.By building two-dimensional transition metal dichalcogenides/graphene heterostructure to obtain better properties has attracted more and more attention from researchers.On the other hand,the electrical and optical properties will be changed after modification of the heterostructuresIn this paper,based on the heterostructures of the two-dimensional transition metal dichalcogenide and graphene and density functional theory,we discussed the changes in electrical and optical properties of the heterostructures by introducing vacancies and doping.The changes of the optical properties have broadened the development of two-dimensional materials and provided useful guidance for the design of new optical nanodevices based on two-dimensional materials.The main achievements are as follows:1.First-principles calculations of graphene/MoS2 heterostructureThe electronic structure and optical properties of graphene/MoS2 heterostructure(GM)were studied based on density functional theory.Compared with single-layer graphene or MoS2,the band gap will increase and the dielectric constant of the GM system will increase.Optical parameters such as absorption coefficient,refractive index,and reflectance will have a certain red shift,but a blue shift will appear in the energy loss spectrum.Electronic structure and optical properties of single-layer graphene and MoS2 are changed after they are combined to form the heterostructure,which broadens the extensive developments of two-dimensional materials.2.First-principles calculations of graphene/WSe2 heterostructureThe effects of W and Se vacancies on the electronic structure and optical properties of GW were studied based on density functional theory.It was found that the formation of heterostructures and the introduction of W or Se vacancies have a great impact on the electronic structure of WSe2.In addition,after introducing W or Se vacancies in the GW,the optical parameters has appeared a large red shift,and the values of the optical parameters are larger than those of the pure GW.In particular,the effect of W vacancies is greater than that of Se vacancies.These theoretical results show that the introduction of vacancies can indeed adjust the electronic structure and optical properties of GW heterostructures,which provides useful guidance for the design of new optical nanodevices based on two-dimensional heterostructures.Based on the density functional theory,we also discussed the electrical and optical properties of graphene/WSe2(GW)heterostructures doped with lanthanides.After doping with lanthanide,red shift appears in the low energy region and the optical parameter values are improved.Different doping types are also discussed.In the case of a single doping,replacing the Yb atom at the W position will greatly improve the peak of the optical parameters.In the case of co-doping,it is found that the effect will be more obvious when the two doped lanthanide atoms are located in second neighboring positon.These results show that lanthanide doping can indeed adjust the electronic structure and improve the optical properties of GW heterostructures,which provides ideas for the design of new optical nanodevices based on two-dimensional materials.