First-principle Analysis Of Donor-acceptor Co-doped TiO₂ And Study On Electrical Properties Of Thin Films

Rutile TiO2 is a typical dielectric material with a binary oxide structure.The ferroelectric phase transition does not occur when the temperature is reduced to OK.Anatase TiO2 is a material with large lattice distortion and can be easily produced at a relatively low temperature.By doping the ferroelectricity of TiO2 with a variety of crystal forms,the good electrical properties can be obtained by changing its crystal structure.Studies have shown that the microstructure of TiO2 can be adjusted through stress,doping and other methods to adjust its electrical properties.In this paper,the structure and electrical properties of the donor-acceptor doped TiO2 are calculated by first-principles to guide later experiments.By exploring the thin film preparation process,a properly doped thin film substrate is obtained,and the amount of doped elements in the thin film is changed to adjust the electrical properties of the thin film.Through the first-principles calculation of rutile TiO2,the effect of different doping ions on the structure and electrical properties of TiO2 was studied.The results show that after doping with V5+-A13+,Nb5+-Al3+and Ta5+-A13+,lattice distortion occurs in the supercell.When V5+-A13+ion doping,the electric dipole moment introduced is the largest,which is 1.4386�10-15D.After Ta5+-A13+,Ta5+-Ga3+and Ta5+-In3+doping,when Ta5+-A13+is co-doped,the energy of the supercell is the lowest,and when Ta5+-A13+doping,the electric dipole moment introduced by doping is the largest,is 1.3511�10-15D.When the radius of doped ions is similar,the electric dipole moment introduced by doping is the largest,and then the radius difference between doped ions and Ti4+is the largest.Through the first-principle calculation of anatase TiO2,in order to ensure the stability of the crystal,the supercell is doped with Ta5+-A13+ions.When the doped ions are doped into the crystal,the energy of the supercell is increased.When the doping ions are farthest away,the energy of the doped TiO2 supercell is the lowest,and the electric dipole moment introduced by doping is 3.6582�10-18D.The titanium dioxide film was prepared by the pulling method.When the colloid concentration was 0.1 mol/L and the annealing temperature was 700?,the crystallinity of the prepared film was still strong when the colloid concentration was small.With the increase of annealing temperature,the prepared film gradually became crystallized.When the annealing temperature was 700?,the crystallinity was the highest.The spin coating method was used to prepare different layers of TiO2 thin films.When the annealing temperature was 700? and the spin coating number was 5,the crystallinity was the highest.The doped(Ta0.5Al0.5)xTi1-XO2 thin film forms an anatase TiO2 crystal phase,and there is no second phase was produced.When the doping content,x=0.005,the film has weak ferroelectricity.With the increase of doping content,the pressure resistance of the film is significantly improved.When the doping content,x=0.02,the voltage that the film can withstand reaches 450 kV/cm,and the maximum polarization strength of the film is 2.47 ?C/cm2.