Effect Of Fe-doping And Point Defect On The Magnetic And Optical Properties Of SnO₂ By First-principle

SnO₂is a significant n-type wide-bandgap semiconductor material with the advantages of low cost,excellent optical performance,and high chemical stability.SnO₂can be made into DMSs by doping an effective transition metal or rare-earth metal.In addition,room-temperature ferromagnetism in DMSs can be enhanced by doping effective magnetic ions.Fe is a suitable dopant with high solubility in SnO₂.DMSs made of transition metal-doped SnO₂are useful in the field of information science.Although domestic and foreign research on magnetic properties of Fe-doped SnO₂has obtained certain progress,the magnetic source of the system remains unclear.Most of the research results are about the effect of Fe doping concentration on the optical properties of SnO₂.The research on the effect of Fe²⁺/Fe³⁺doping on the magneto and optical properties of SnO₂is still lacking.Therefore,this article uses the CASTEP module of Materials Studio8.0.Based on the density functional theory,the generalized gradient approximation plane wave supersoft pseudopotential method theoretically studies the effects of Fe doping and point defects(V_O,V_Sn)and Fe valence on the magneto-optical properties of SnO₂.To resolve the controversy of the magnetic source of Fe-doped SnO₂system,pure Sn₁₆O₃₂,Sn₁₅Fe O₃₂,ten different Fe-V_Ospacing Sn₁₅Fe O₃₁and five different Fe-V_Snspacing Sn₁₄Fe O₃₂supercell models were constructed by first-principals.The total energy,magnetic moment,band structure and density of states of the constructed system were calculated.Calculation results show that Fe-doped SnO₂with V_Oor V_Snexhibit long-range ordered ferromagnetism and Curie temperature above room temperature.The system has different magnetic properties with different doping modes,which are beneficial to the magnetic adjustment of dilute magnetic semiconductor?DMS?.The double exchange effects among the electrons of O-2p and Fe-3d states are the origin of ferromagnetism in Sn₁₅Fe O₃₁.Similarly,ferromagnetism in Sn₁₄Fe O₃₂is derived from the double-exchange effects among the electrons of O-2p and Fe-3d states.These effects are produced by hole carriers after complexes form by Fe doping and V_Oor V_Sn.Simultaneously,Results also show that the decreased distance between Fe and vacancies(V_Oor V_Sn)lowers formation energy and thus increases the system stability.In order to study the effect of Fe²⁺/Fe³⁺doping on the magneto and opticalthree different Fe³⁺-Fe³⁺spacings of Sn₁₄[Fe³⁺]₂O₃₂supercell model were constructed.First-principles calculations revealed that Fe²⁺/Fe³⁺doping significantly redshifts the absorption spectral,induces spin-polarized impurity bands near the Fermi level,and leads to evident spin polarization phenomenon.Fe²⁺and Fe³⁺exhibit different effects on the electronic structures and magneto and optical properties of the doped system.Specifically,Fe³⁺doping enhances the dominant role of p-d exchange interaction and the Fe³⁺doped systems are likely to obtain high Curie temperature and magnetic moment at the same doping concentration and position;moreover,the imaginary part and absorption spectrum of the dielectric function of Fe²⁺-doped SnO₂systems have large new peaks in the low-energy region,which are attributed to electronic transitions from the spin-polarized impurity levels to the conduction band.Through the first-principles study,we reasonably explained the magnetic origin of the Fe-doped SnO₂system,confirmed the influence of different valence states Fe on the electronic structure and magneto and optical properties of the SnO₂system.This has a theoretical guiding significance for the application of Fe-doped SnO₂photocatalysts and diluted magnetic semiconductor.