Investigation Of The Electrical And Optical Properties Of Barium Titanate Ferroelectric Thin Film Heterostructures

In recent years,with the rapid development of science and technology,the demand for materials with special properties is increasing day by day,and higher requirements are put forward for their properties.Researchers also make continuous efforts to study,in order to get materials with better properties.Barium titanate,the first pero vskite ferroelectric material with oxygen octahedral structure,has not only simple structure,but also ferroelectric,dielectric,piezoelectric,pyroelectric,electro-optical and nonlinear optical effects.It is one of the important functional thin film materials,so it is a hot thin film material for researchers to study.Researchers use various methods to improve one aspect of its performance,and then apply it to devices to produce film devices with stronger performance.In this paper,the sol-gel method with low cost and easy control of process parameters was used to prepare barium titanate films.By controlling the process parameters and boundary conditions of the films,the microstructure of barium titanate films could be precisely controlled.Barium titanate thin films were prepared on different transparent substrates.The barium titanate film was prepared,the transmittance was measured,and its optical band gap was calculated.Two kinds of heterostructures for barium titanate ferroelectric thin film plate capacitors were prepared by using optimized process parameters.The microstructures of the films were characterized and the electrical properties were tested,and then the structure-activity relationship was obtained.The main research contents of the paper are as follows:(1)The influences of deionized water ratio and sol concentration in the sol configuration process on the surface morphology and crystallinity of the BTO films were investigared,the optimal water-adding ratio and sol concentration was estimated to 1:15 and 0.5 mol/L,rexpectively.(2)The influences of annealing time,annealing mode,annealing temperature and thickness on the crystallinity,surface morphology and electrical properties of the films were studied,and the optimal annealing process parameters were obtained: drying at 100 ℃ for 5 min,pyrolysis at 350 ℃ for 5min and annealing at 700 ℃ for 10 min in a tubular furnace layer by layer,with a total of 8 layers of rotary coating.(3)The LNO oxides on silicon substrates were prepared by chemical solution spin coating method.The effects of chemical solution configuration,sol concentration and film thickness on the crystal structure and surface morphology of the films were studied.The results show that high quality LNO oxide thin films are prepared by spin-coating 6 layers of LNO sol with a concentration of 0.3 mol/L,which is dried for 5 minutes at 200 ℃,pyrolyzed for 5 minutes at 400 ℃ and annealed for 10 minutes at 700 ℃ in a tubular furnace,and used to fabricate BTO/LNO heterostructure ferroelectric thin film capacitor devices.(4)Two kinds of BTO film capacitors with heterogeneous structures of d ifferent bottom electrodes were prepared,and their structures were Au/BTO/LNO/Si and Au/BTO/Pt/Si respectively.The crystal structure,microstructure and electrical properties of Au/BTO/LNO/Si under vacuum annealing and air annealing were studied.Au/BTO/LNO/Si and Au/BTO/Pt/Si both heterostructure was 550,600,700,800,900 and 1000 ℃ for different temperature annealing of BTO.Find two structures is under 800 ℃ iron electric properties and dielectric properties is the best;The ferroelectric properties of Au/BTO/LNO/Si are slightly better than the latter,but the pressure resistance is worse than the latter.Au/BTO/Pt/Si structure has better dielectric performance,stronger pressure resistance,better ferroelectric temperature stability and better dielectric stability.(5)Crystalline and amorphous BTO thin films were prepared on transparent substrates.The transmittance of JGS1-based crystalline BTO thin films prepared with different sol concentration was measured by spectrophotometer,and their optical band gaps were calculated.It is found that the optical band gap of crystalline BTO films decreases with the increase of sol concentration.The transmittance of amorphous BTO films prepared on JGS1 is higher than that of crystalline films,and the optical band gap is larger.The transmittance of amorphous BTO thin films with different thickness was measured,and the optical band gap of amorphous BTO thin films was calculated.It was found that the optical band gap of amorphous BTO thin films increased with the increase of thickness.