Study On Electronic Structure And Optical Properties Of Cr And W Co-doped Monolayer MoS₂

Material systems can usually be divided into zero-dimensional,-dimensional,twodimensional and three-dimensional systems.Among them,researchers have paid close attention to the excellent characteristics of two-dimensional layered materials in electrical,optical and catalytic aspects.Graphene materials are currently the most widely studied and most studied two-dimensional material systems.However,due to the limitations of graphene materials due to the characteristics of zero band gap,exploring new twodimensional materials has become a new research topic.Two-dimensional chalcogenides have attracted wide attention because of their environmental friendliness,abundant reserves and excellent electronic properties.Among them,the research on molybdenum disulfide has become a hot research field for researchers.This is mainly due to its layered structure similar to graphite and very stable chemical properties,so it has huge fields in optics,electricity,and friction lubrication.Application value and market value that can be tapped.In order to explore more uses of layered molybdenum disulfide matrix materials in the field of optoelectronics,this paper uses the first principle based on density functional theory,through the CASTEP module simulation calculation in the Materials Studio software package,using doping In order to change the electronic structure and optical properties of molybdenum disulfide by changing the doping method and the occupation method,the performance of the material in the application field is changed to achieve the purpose of widening its application.The main work completed is as follows:First complete the establishment of models of different systems,and then through the preliminary calculation of CASTEP module,we get the total energy of different systems,and then through the formation energy calculation formula we know that: For Cr,W single doped system and total For the doping system,the formation energy of the doping system is less than zero,which is-0.66 eV,-1.66 eV and-2.24 eV,respectively.The value has no effect,and the formation energy is-2.24 eV.All of the established doping systems can form spontaneously under natural conditions and exist steadily in nature.The electronic structure and optical properties of Cr,W single-doped MoS₂ system were calculated.According to the results of electron band structure diagram and state density diagram,we know that both intrinsic and doped MoS₂ systems are direct bandgap semiconductors,with bandgap widths of 1.811 eV,1.312 eV,and 1.794 eV,respectively.Among them,Cr doping has a greater influence on the band gap width of the MoS₂ system.At the same time,the contribution of the conduction and valence band electron orbits is determined.Compared with the intrinsic MoS₂ system,the doped system has more complex electromagnetic absorption capacity of the dielectric function,the electronic transition energy of the conduction band and the valence band,the absorption edge in the absorption line and the conductivity of the system under different incident photon energies.The big difference is similar to the electronic structure.Cr doping has a greater influence on the optical properties of the system,which may be due to the closer atomic structure of the W atom and the Mo atom.The electronic structure and optical properties of three different space-occupying codoped MoS₂ systems were studied.The electronic structure research results show that the interphase space-occupying doping system is a direct band gap semiconductor,and the band gap width is between the middle values of the two single doping systems.The other two co-doping systems are indirect band gap semiconductors,and the forbidden band width is much lower than the interphase space-occupying doping system.This may be caused by the weak interaction between Cr atoms and W atoms in the interphase spaceoccupying doping system.The optical properties of the separated space-occupying and adjacent space-occupying doping systems have different degrees of blue shift compared to the the interphase space-occupying doping system,which is mainly due to the fact that the separated space-occupying and adjacent space-occupying doping systems are indirect band gap semiconductors.