Impurity Effects On The Electronic Structures And Magnetic Properties Of Monolayers PtSe₂

Graphene has rapidly developed into a hot topic of emerging materials due to its unique properties since graphene was successfully peeled off in 2004.Subsequently,two-dimensional nanomaterials,as a new star among emerging materials,have also attracted attention due to their unique physical and chemical propertiesas.Among them,transition metal chalcogenides have excellent magnetic,electrical,and thermodynamic properties,and are widely used in electronic and optoelectronic devices,spintronic devices,and integrated circuits.In this article,first-principles methods based on density functional theory are used to study the electronic structure and magnetism of monolayer PtSe₂.The lattice constants,formation energies,and band structures of non-metallic atoms(N,P,As)doped and co-doped with non-metallic elements and transition metal elements are calculated.The main results obtained are as follows:(1)Investigate the effects of non-metal atoms X=N,P,As(doping concentration of 3.125%)on the electronic structure and magnetism of monolayer PtSe₂.The calculation results show that the total energy and formation energy of the doping system are closely related to the radius of the doping atoms.The formation energy increases with the increase of the atomic radius.By comparing the formation energy under different experimental conditions,it is known that substitutional doping is easier to carry out under the experimental conditions of Pt-rich.The research results indicate that N,P and As atoms can effectively regulate the p-type doping of the monolayer PtSe₂.Further analysis of the magnetic properties shows that the systems doped with N,P,and As atoms all show magnetism and are magnetic semiconductor materials.(2)We select the most stable N doping system to study the effect of strain on its electronic structure and magnetism among the above doping systems.The investigation results indicate that the system has p-type doping under the strain from-6%to 13%.The magnetic moment of the system is 0.542?_Bunder no strain.The magnetic moment changes under the action of different strains,but the maximum magnetic moment is 0.782?_Bat-6%strain.In addition,the band gap keeps getting smaller as the tensile and compressive strains continue to increase.Meanwhile,the positions of the bottom of the conduction band and the top of the valence band have also changed under the action of strain,but the system has maintained the characteristics of an indirect band gap semiconductor.(3)Investigate the influence of non-metal atoms X=N,P,As(Pick two X atoms,doping concentration is 6.25%)on the electronic structure and magnetism of monolayer PtSe₂.The calculation results show that the bond length of Pt-X increases with the increase of the X atomic radius.Except for the third nearest neighbor N-doping system which is a direct band gap semiconductor,the other doping systems are indirect band gap semiconductor materials.All doping systems keep semiconductor properties,which means that the introduction of X atoms does not change the semiconductor properties of the monolayer PtSe₂at a doping concentration of 6.25%.(4)For the co-doping of different non-metal atoms and transition metal atoms,we only analyzed the system with the lowest total energy:the first neighbor Mn-N,the second neighbor Mn-P and the third neighbor Mn-As co-doped.The calculation result shows that the total magnetic moment of the Mn-N co-doped system is smaller than the first nearest neighbor N-doped magnetic moment.However,the total magnetic moment of the Mn-P co-doped system is greater than that of the second neighbor P-doped system.The magnetic moments derived from Mn atoms in above two systems are 1.544?_Band 1.655?_B,respectively.The introduction of Mn atoms in the Mn-As co-doped system not only induces magnetic moment,but also transforms the As doping system from non-magnetic semiconductor to magnetic metal.Moreover,the magnetic moment provided by Mn atoms in Mn-As co-doping is 2.367?_B.We found that the Mn-N and Mn-P co-doped system is still magnetic semiconductor material,while the Mn-As doped system is transformed from semiconductor to magnetic metal.