The Adjustment Of Defects On The Electromagnetic Properties Of Transition Metal Chalcogenides

MoS2 and ReS2 are two typical transition-metal sulfides.In recent years,monolayer MoS2 has become a research hot spot because of its successful application in nano-electronic devices.Monolayer MoS2 is a typical semiconductor with a direct band gap of 1.8 eV compared to the zero band gap of intrinsic graphene,which will enable it to have a wider range of applications than graphene in nano-electronic devices.Based on the first-principle calculations,researchers can see that the transistor based on MoS2 has such excellent characteristics as low power consumption,large transconductance and large ON-OFF current ratio.As the research continued,researchers began to study its one-dimensional structure.Recently,various research teams around the world have successfully prepared MoS2 nanoribbons in different ways.Its unique properties and potential application in nano-electronic devices make it a hot research topic.In addition,ReS2 is a semiconductor,the band gap of which is direct and is independent of the number of layers.However,it does not get ordered magnetism.How to realize the ordered magnetism of ReS2 is also a research hot spot.Based on the above considerations,in this paper,we will use the first-principle calculations to study the adjustment of electromagnetic properties of defects on MoS2 nanoribbons and ReS2 nanosheets.The main contents are as follows:(1)Firstly,we performed density functional theory calculations to investigate the electronic and magnetic properties of zigzag MoS2 nanoribbons with an S vacancy(ZMoS2NRs-Vs).The systems are all magnetic with magnetism concentrated on the edge Mo and S atoms.Interestingly,passivation of functional groups such as H,F,OH or NH2 with a passivated concentration of 25%can not only provide half-metallicity in ZMoS2NRs-Vs but also enhance the stability of the system.These diverse electronic and magnetic properties might open great opportunities for MoS2 materials in spintronics in the future.(2)Then,we continue to study the electronic structure,magnetic properties and stability of zigzag MoS2 nanoribbons with an S vacancy(ZMoS2NRs-Vs)by density functional theory and considered their different edge passivation.The ZMoS2NRs-Vs systems are magnetic metals with ferromagnetic(FM)edge states.The magnetic moments are strongly influenced by the site of S vacancy and edge passivation because the vacancy and edge states significantly change the structure of the systems.Importantly,we can achieve distinct FM states such as both edge FM and single edge FM states in the ZMoS2NRs-Vs by tuning edge passivated pattern.Additionally,edge passivation can not only tune the magnetism of the ZMoS2NRs-Vs but also enhance their stability by eliminating dangling bonds.These interesting findings on the ZMoS2NRs may open the possibility of their application in nanodevices and spintronics.(3)After that,based on density functional theory(DFT)calculations,we have investigated the electronic structure,magnetic properties and stability of transition-metals(TM)doped two-dimensional(2D)1T' phase ReS2.TM doping can tune ReS2 from the nonmagnetic semiconductor to magnetic semiconductor.The magnetism concentrates on dopant TM and neighbouring Re and S atoms,which mainly comes from competition between the exchange splitting and crystal-field splitting.More importantly,Co-doped ReS2 may be a promise diluted magnetic semiconductor(DMS)owing to its strong ferromagnetism with long-range ferromagnetic(FM)ordering,high Curie temperature above room temperature and good stability.Finally,we summarize the research content of this paper,and put forward some questions and prospects for future research.