Preparation And Photoelectric Properties Of Barium Strontium Titanate Perovskite Films

Barium strontium titanate（BST）has high transmission,low absorption,high refractive index and other optical properties in the visible light range and is widely used in highly integrated optical devices.The A-site and B-site doping can change the lattice structure of the material,thereby changing the electrical and optical properties.However,most of the research has focused on its electrical performance,and there are few systematic studies on the optical performance of BST.This paper uses barium strontium titanate（BST）as the research substrate,and simulates the A-site strontium ion(Sr²⁺)doping through Materials Studio to explore the effects of different content of strontium doping,ordered substitution and oxygen vacancies on the structure and performance of BST.At the same time,the influence of B-site zirconium(Zr⁴⁺)and cerium(Ce⁴⁺)doping on structure and performance is studied.The B-site zirconium and cerium doped Ba_0.5Sr_0.5TiO₃ powder was prepared by solid-state reaction,and the influence of sintering temperature on the optical properties of the powder was studied.The BST target was prepared,and the corresponding thin film was prepared on the fused silica substrate by laser pulse deposition（PLD）,and the effect of A-site strontium doping on optical properties,especially refractive index,was explored.First,construct the supercell structure of Sr²⁺disorderly doped barium titanate（BT）.The results show that with the increase of strontium content,the lattice parameter of BST decreases,the band gap increases from 1.742eV to 1.841eV,and the optical performance changes.The calculation of Sr²⁺ordered doped BT shows that the structure of BST changes from the tetragonal phase structure of[100]and[110]to the cubic phase structure of[111]orientation,and the lattice parameter increases from 3.982?of[100]orientation to the[111]orientation 3.985?.Simulate the effect of oxygen vacancies on the structure and optical properties of BST.With the generation of oxygen vacancies,the lattice parameter of BST decreases from 3.984?to 3.902?.The dielectric function and refractive index of the material increase,and the dielectric loss,reflection,absorption and photoconductivity decrease.Secondly,Zr⁴⁺doping will increase the lattice parameter of barium strontium zirconate titanate（BSZT）from 3.982?of BST to 4.473?of barium strontium zirconate（BSZ）.The forbidden band width increased from 1.787 eV to 2.632 eV,and the dielectric function increased from 2.45 to 2.64 and finally to 1.26.The refractive index first increased from 1.57 to 1.63 and then decreased to 1.12.The reflection,absorption,dielectric loss and photoconductivity all increase first and then decrease.Ce⁴⁺doping increases the lattice parameter of cerium barium strontium titanate（BSCT）from 3.982?to 4.452?.The band gap increased from 1.787 eV to 2.672 eV,the dielectric function decreased from 2.25 to 1.27,the refractive index decreased from 1.5 to 1.13,and the reflection,absorption,dielectric loss,and photoconductivity decreased.Then,the Zr⁴⁺and Ce⁴⁺doped BST powders were prepared by solid-state reaction,and the influence of sintering temperature on the powder structure and properties was studied.When Zr⁴⁺is doped,the absorption of the powder in the range of 400nm to 880nm is close to 0.After the sintering temperature of the powder is increased,the absorption in the range of 400nm to 650nm is increased,and the absorption edge appears with the increase of Zr⁴⁺doping has a blue shift.The transmittance is as high as 95%.After the sintering temperature is increased,the transmittance of some component powders is reduced.With the increase of Ce⁴⁺content,the absorption of the powder has a red shift.With the sintering temperature increasing,the absorption of the powder is increased.Finally,the BST target was prepared by the solid-state reaction and the corresponding thin film was prepared by PLD technology.The transmission,absorption and refractive index of the film were tested with a dual-beam UV-visible spectrophotometer.The BST film has high transmission and low absorption characteristics in the visible light range,and the refractive index can be adjusted between 1.86 and 2.05.