Effect Of Charge On Amorphous Oxide Atom And Electronic Structure Properties

Amorphous oxide materials have a wide range of applications in solid electronic materials,such as sensor solid state memories,photodiodes,and microelectronic CMOS devices.Oxygen vacancy defects are often introduced into amorphous oxides.The presence of charged oxygen vacancies can have an important effect on the atomic structure and electronic structure of amorphous oxides.In this dissertation,the amorphous structure was generated by molecular dynamics,and the electronic structure and defect formation energy of the charged defect system were calculated by the density functional theory.The theoretical calculations show that the charged oxygen vacancy defects have a defect state in the bandgap and pass through the system.The analysis of the split-wave density of states shows that the defect states originate from atoms near the defects.At the same time,the formation energy of charge defects was calculated and the stability of these defects was compared.Firstly,the molecular dynamics simulations heat up to the melting point of crystals such as SiO₂,Al₂O₃,MgO,HfO₂,TiO₂,and ZrO₂,and the amorphous oxide structure is obtained by rapid cooling and cooling,and the amorphous structure is optimized.An oxygen atom is removed from the amorphous oxide to form a vacancy defect,and the system is charged.Based on this,the defect system is relaxed to obtain the influence of the charge defect on the bond length and the bond angle between the amorphous oxide atoms.When the oxygen vacancy defect is+2,+1,-2,-1,the Si-O bond length near the defect becomes larger,its relative variation is between 5.80 and 11.67%,and the O-Si-O bond angle becomes smaller.Relative changes range from-18%to-2%,and the relative changes in bond length and bond angle are minimal when in the neutral state.In the amorphous Al₂O₃,the Al-O bond length near the defect and the bond angle increase also decrease,which is much smaller than the relative change of the SiO₂ bond length.When the oxygen vacancy defect is+2,+1,Al The relative changes of-O bond length are-4.997-0.7014%,-3.35-1.78%,and the relative changes of O-Al-O bond angles are-14.69-12.43%and-5.65%-4.60%,respectively,except for two abnormal ones.The bond lengths of Al-O and O-Al-O bonds decrease and the bond angle increases.When the oxygen vacancy states are 0,-1,and-2,the change of Al-O bond length is just as good as Contrary to the positive valence state,most of the Al-O bond lengths increase,and the O-Al-O bond angle decreases.In the amorphous SiO₂,when valences of defects are+2 and-2 in SiO₂,deep defect levels are generated in the band gap;When the valence states are+1,0,-1,deep defect levels are generated near the top of the valence band,and shallow defect levels are generated near the bottom of the conduction band.The defect energy levels generated by the charge defects in the amorphous SiO₂ mainly come from the Si and O atoms near the defects.The Si 3s and 3d orbits have a large contribution to the defect energy level,while the Si 3d orbit has a slight contribution,while the O 2p orbit also contributes,but the contribution is small.In the amorphous SiO₂,the corresponding defect formation energies when the valence states of the defects are+2,+1,0,-1,and-2respectively are 6.02 eV,5.67eV,5.55eV,12.20eV,and 19.97eV,the defects of the-2,-1,and 0 valences are stable in the amorphous SiO₂ structure.In amorphous Al₂O₃,when the valence of the defect is+2,+1,0,-1,-2,the defect formation energy is-2.80eV,1.58eV,6.69eV,15.15eV,24.42eV,in which the defect of valence states of+2,+1,and 0are stable in amorphous Al₂O₃.The HSE hybrid functional modification of the defect formation energy and the thermodynamic conversion energy level of the DFT's PBE functional calculations,the HSE hybrid functional gives a more reliable result.