Study On The Electromagnetic Properties Of Rare-earth Metal Doped Two-dimensional ZnO And WS₂

In recent years,in the field of vigorous development of spintronics,the search for dilute magnetic semiconductor materials with practical value has received extensive attention from the scientific community.Since the discovery of two-dimensional graphene,two-dimensional metal oxides and transition metal disulfides with graphene-like structures have attracted particular attention.Its large band gap,unique geometric configuration,wide band gap and stability make this kind of structure convenient to be doped and conducive to nanocrystallization.Therefore,they have a broad development prospect in the field of nano electronic spin devices in the future.The rare earth element has strong electron locality and the magnetic moment can be induced effectively by introducing this kind of atom.Based on density functional theory and using CASTEP module of Materials Studio（MS）software,we systematically investigate the effects of rare-earth metals La,Ce,Pr,Nd,Pm,Sm and Eu doping on the electromagnetic properties of two-dimensional ZnO and WS₂.Due to the strong electron localization of rare-earth metals,U value is introduced to correct the errors caused by self-interaction in strongly correlated systems.The main research contents and results of this paper are as follows:（1）Study on the electromagnetic properties of rare-earth metal doped two-dimensional ZnO.By the Materials Studio software,firstly,the intrinsic two-dimensional ZnO model is constructed.Then,the related properties are calculated.In the optimized two-dimensional ZnO,the zinc position is replaced by a rare-earth metal atom.The relaxated structure and electromagnetic properties of the doping systems are calculated.According to the results of formation energy,it is theoretically proved that rare-earth metal doped two-dimensional ZnO can be synthesized experimentally.Part of the electrons of the rare-earth atoms in the doping systems transfer to the adjacent O atoms.The rare-earth metal doped two-dimensional ZnO can reduce the band gap compared to the intrinsic ZnO monolayer.The La-doped two-dimensional ZnO system does not have magnetism,and other rare-earth metal atom doping systems present magnetic moments,which are mainly contributed by unpaired f electrons.Therefore,the f orbitals of rare-earth atoms are particularly critical to the electromagnetic properties of two-dimensional ZnO.（2）Study on the electromagnetic properties of rare-earth metal doped two-dimensional WS₂.The intrinsic two-dimensional WS₂ supercell model is constructed and geometrically optimized.The rare-earth metal atoms of La,Ce,Pr,Nd,Pm,Sm and Eu are selected to replace one W atom in the optimized two-dimensional WS₂.The electronic structures and magnetic properties of seven different doping systems are investigated.According to the formation energy calculations,it is found that these rare-earth atoms doped WS₂ systems are more stable under S-rich than W-rich conditions.Rare-earth metal doping can regulate the electronic structure of two-dimensional WS₂.The impurity band appears near the Fermi level,the band gap of the system decreases,the energy band structure of spin up and spin down loses symmetry,and the system generates magnetic moment.With the increase of atomic number,the charge transfer of rare-earth atoms in the doped system gradually decreases,and the magnetic moment of the doped system gradually increases.The magnetic moment of Eu doped two-dimensional WS₂ is as high as 9.10μ_B.The doped systems are all magnetic,and the magnetic moment is large.The density of states and charge distribution of the system are discussed and analyzed.It can be seen that the magnetic moment of the doped system is mainly contributed by the unpaired 4f electrons of the rare-earth atoms,the neighboring W atoms and the neighboring S atoms.This is different from the magnetic mechanism of rare-earth metal doped two-dimensional ZnO.It can be seen that rare-earth metal doping has a regulatory effect on the electronic structure and magnetic properties of two-dimensional WS₂.In summary,the doping of rare-earth metals can effectively regulate the electromagnetic properties of two-dimensional ZnO and WS₂,and induce the system to generate magnetic moments.Both types of doping systems are expected to become a new generation of diluted magnetic semiconductor materials.