First-principles Investigation On The Effects Of Doping And Strain On The Magnetic And Optical Properties Of Two-dimensional SnO

Two-dimensional SnO is a new type of two-dimensional semiconductor material with wide band gap,good stability,high carrier mobility and non-toxicity.It has broad application prospects in the field of nano-electronic devices and optoelectronic devices.At present,SnO nanowires and thin layer materials have been successfully prepared experimentally.Studies have shown that two-dimensional SnO has a high hole mobility(641 cm² V^-11 s^-1)and is a stable p-type two-dimensional semiconductor material,but its intrinsic non-magnetic properties greatly limit the application of SnO in spintronic devices.Therefore,the first-principles calculations method is used to study the non-metal and 3d transition metal element doping of two-dimensional SnO,and the electronic structure and optical properties of two-dimensional SnO under biaxial strain conditions are studied in this paper.Firstly,the influence of substitution doping of 3d transition metal?TM?elements?Sc-Zn?on the electronic structure and magnetic properties of monolayer SnO has been studied using the first-principles calculations of spin polarization density functional theory?DFT?.In order to ensure the reliability of the calculation,we first theoretically calculated the electronic structure,energy band and electronic density of the two-dimensional SnO primitive cell.The calculated results show the two-dimensional intrinsic SnO does not show magnetism and the magnetic properties can be induced by monolayer SnO doped with with transition metal atom Sc,V,Cr,Mn,Fe,Co or Cu,and the magnetic moment is determined by the type of dopant atoms.The magnetic moment of the system doped with Sc,Co or Cu atom is 1?_B,the magnetic moment of the system doped with V or Mn atom is 3?_B,and the magnetic moment of the system doped with Cr or Fe atoms is 4?_B.Through the study of the energy band and the partial densities of states of transition metal doping system,it is found that new impurity energy levels appear in the forbidden band of the monolayer SnO after doping transition metal atoms,the magnetic moment is mainly derived from transition metal atoms to 3d orbital electrons,and partly from the hybridization between the it and the 2p orbitals of the adjacent O atoms.Secondly,the influence of substitution doping of non-metallic elements?H,B-F,Si-S,As,Br,I?on the electronic structure and magnetic properties of monolayer SnO has been studied using the same calculations method.The calculated results show the magnetic properties can be induced by monolayer SnO doped with the non-metal atom B or N,and that the magnetic moments are0.84?_B and 0.44?_B,respectively.In the B-SnO doping system,the magnetic moment is mainly derived from the hybrid coupling of B-2p orbital and the adjacent Sn-5p orbital.In the N-SnO doping system,the magnetic moment mainly stems from the hybrid coupling of Sn-5p,O-2p and N-2p orbitals.Further study on the magnetic coupling of two B or two N atoms doped single-layer SnO shows the C₁ configuration of SnO supercell doped with double B atoms is the most stable,that the C₄ configuration of SnO supercell doped with double N atoms SnO supercells is the most stable,and that both of them exhibit paramagnetism.The calculated formation energy shows that the two-atom doping can be easily realized under Sn-rich environment.These theoretical results will provide a theoretical reference for the potential applications of doping SnO monolayer in optoelectronic and spintronic devices.Finally,we explored the effects of different biaxial strains on the electronic structure and optical properties of two-dimensional SnO materials.The energy band structure,density of states and dielectric function of the crystal were calculated,and the optical constants of the crystal were obtained by the dispersion relation.The results show that when there is no strain,two-dimensional SnO is a semiconductor with a wide and indirect band gap.The application of biaxial strain can narrow the two-dimensional SnO band gap,and the biaxial tensile strain is compared with the biaxial compression strain,the effect on the electronic structure of two-dimensional SnO is more obvious.When the photon energy is 0²0eV,the optical spectra of the complex dielectric function,absorption coefficient,energy loss function and extinction coefficient of single-layer SnO are greatly affected by biaxial strain.The biaxial compressive strain causes all the peak positions of these optical spectra to move toward the low energy direction,and the first peak rises;and the biaxial tensile strain causes all the peak positions of these optical spectra to move toward the high energy direction,and the first peak decreases.At the same time,the biaxial compressive strain increases the static dielectric constant,the static refractive index and the reflectivity of the two-dimensional SnO,and the tensile strain reduces them.Compared with the biaxial tensile strain,the biaxial compressive strain on the electronic structure of two-dimensional SnO is more obvious.Studies have shown that biaxial strain can effectively regulate the electronic structure and optical properties of two-dimensional SnO.