First-principles study of alkaline earth metal X(X =Be,Mg,Ca and Sr)doped two-dimensional SnS2 materials
Based on the first-principles study of pseudopotential plane wave method,the electronic structures,magnetic properties and optical properties of alkaline earth metal X(X =Be,Mg,Ca and Sr)doped two-di-mensional(2D)SnS2 monolayers were calculated.The results show that the systems under S-rich condition are more stable than those under Sn-rich one,and the Ca and Sr doped systems have the smallest formation ener-gies of respectively-2.674 eV and-2.422 eV under S-rich condition.The band structures show that after Be doping,the impurity levels appear in the spin-down channel near the Fermi level,which lead to the transi-tion of the SnS2 system from a completely symmetric non-magnetic semiconductor to a magnetic semiconductor with a magnetic moment of 1.999 μB.After Mg doping,the system transforms into a non-magnetic P-type semiconductor.Due to the different polarization degrees of Ca and Sr doped systems,the band structure of the spin-down channel passes through the Fermi level,however,the energy band of the spin-up channel does not pass through the Fermi level,showing semi-metallic properties with magnetic moments of 1.973 and 2.000 μB,respectively.At the same time,it is found that X doped systems exhibit excellent optical properties.The real part of dielectric function is greatly increased,and the polarization ability is enhanced.The value of the imagi-nary part becomes significantly larger in the low-energy region,which is more suitable for long-wavelength op-toelectronic devices.Be,Mg,Ca,and Sr doped systems not only lead to a red-shift of the absorption edge,but also improve the effective utilization in the infrared region.
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