Research On The Optical And Magnetic Properties Of Indium Oxide And Its Mo-doped Semiconductors

In2O3 has been widely used because of its good optical and electrical properties.Recently,studies have shown that the undoped In2O3 film after high-temperature vacuum annealing and the molybdenum-doped In2O3(IMO)film prepared at a higher substrate temperature both exhibit room temperature ferromagnetism.In2O3-based semiconductors were reported to room temperature ferromagnetism,which made In2O3 materials with both semiconductor properties and magnetic properties once again aroused widespread attention and research,but there is still controversy about the origin of its magnetic properties.In addition,there is no systematic calculation and analysis on the optical properties of systems containing intrinsic defects.This article focuses on first-principles calculations,supplemented by experiments,to investigate the optical properties and magnetism properties of In2O3 and IMO.Firstly,the optical properties of In2O3 with intrinsic point defects and IMO with different doping concentrations were calculated by first principles.The calculation results shown that,different point defects were introduced into the In2O3 system,except for the Oi-containing system,the systems with VO,VIn and Ini have new absorption peaks of different intensities in the visible light energy range,which indicated that the intrinsic defects will affect the visible light transparency of In2O3.Compared with pure In2O3,Mo doping produced a new absorption peak in the low-energy region,and the light absorption spectrum red-shifts to the low-energy direction.Secondly,different argon and oxygen gas compositions In2O3 films were deposited by magnetron sputtering,it shown that the optical bandgap first decreases and then increases with the increased of oxygen content.The minimum band gap is 3.847eV when Ar:O2=5:2.The In2O3 films annealed in air,as the annealing temperature increased,the oxygen vacancy decreases,and the band gap decreases from 3.802eV to 3.645eV.It shown that the preparation conditions will affect the defects in the deposited sample and thus the optical properties of the film,which is consistent with the theoretical calculation results.And IMO films with different Mo doping concentrations were prepared by magnetron co-sputtering method.The doping introduces free carriers,the carrier concentration increases,and the band gap increases compared with undoped.Then,VASP was used to calculate the electronic structure and magnetic properties of the system when In2O3 contains intrinsic defects with different charge states.The calculation results shown that VO+,VIn0,VIn1-,VIn2-,Oi and VIn+Vo defects can all introduce spontaneous polarization moments.Further magnetic coupling studies have shown that the ferromagnetism of undoped In2O3 may be derived from VIn1-,VIn2-,Oi and VIn+Vo.Finally,the magnetic properties of the IMO system and the influence of neutral intrinsic defects and strains on the magnetic properties were calculated.With the increased of the doping concentration,the magnetic properties of the system increased.As the relative distance of doped Mo atoms increased,the magnetization energy decreased from 56.9meV to 6.21meV,the systems all shown a ferromagnetic ground state,which indicated that the IMO system tends to be coupled to the nearest neighbor ferromagnetic.The nearest neighbor configuration introduces intrinsic defects of Vo,Oi,Vin and Ini respectively,the magnetization energies are 107.29meV,2.21meV,0.24meV and-703.72meV,respectively.Except that the Ini-containing system transforms into an antiferromagnetic ground state,the others still exhibit ferromagnetic coupling,it shown that different intrinsic defects have a regulatory effect on doping magnetism.When a 6%tensile strain was applied to the IMO system,the magnetic moment suddenly changes to 0?B,and the strain can modulate the magnetism of the IMO system.The magnetism of the IMO system is mainly derived from the hybridization of doped Mo atoms and adjacent O atoms.