| Bi3.i5Nd0.85Ti3O12(BNT)is a bismuth layered perovskite structure of ferroelectric materials and is dedicated to researchers because of its lead-free, have higher residual polarization value, high fatigue resistance, high Curie temperature. BNT ferroelectric thin films are widely used in the manufacture of non-volatile ferroelectric random access memory, so the stand or fall of BNT ferroelectric thin film performance directly affects the strengths and weaknesses of the ferroelectric memory performance. LaNiO3 (LNO) conductive oxide is constraint perovskite structure, and BNT thin film is perovskite structure.They are very similar, so the BNT ferroelectric thin film can match growth with LNO thin film. LNO thin film has well electric conductivity, and LNO conductive oxide as a bottom electrode has a broader space. BNT ferroelectric thin film of the heat treatment process, the choice of the bottom electrode on the iron electric properties, is influence the fatigue resistance and leakage current performance very big. The BNT ferroelectric thin film and LNO conductive oxide electrodes are the object of study in this article, and the heat treatment process, doping of Au/BNT/LNO/Si (100) capacitor structure are researched, and discussed the influence of crystal, surface morphology, electric properties, fatigue resistance and the leakage current density. The merits of the BNT ferroelectric thin film performance is compared with LNO bottom electrode and bottom electrode for Pt. The contents and results are the following points:(1) With Ni (CH3COO)2·4H2O, La (NO3)3·6H2O as raw materials, CH3COOH as solvent, the Sol-Gel process can prepare the LNO Sol successfully.The spin coating method is used to prepare LNO conductive oxide film on the Si (100)substrate, become the structure of LNO/Si (100). Different annealing temperature and different annealing time were studied respectively, and the crystal properties and resistivity of LNO thin films are researched. It is found that the annealing temperature is 680 ℃, the annealing time is 60 min, under the conditions the crystallization of the LNO thin film is best and the resistivity is lowest about 1.5 × 10-3 Ω·cm.Under this condition the LNO thin film surface density, smooth and level off, the surface roughness of root mean square value is 1.5 nm. The substrate is able to meet as a bottom electrode of BNT ferroelectric thin films.(2) Spin coating method is used to prepare BNT ferroelectric thin films on the LNO/Si (100) substrate, become the structure of BNT/LNO/Si (100). Different anneal temperature and different annealing method are studied, and the influence of the crystal structure, surface morphology and electrical performance for BNT/LNO/Si(100) structure ferroelectric thin film is studied. It is found that the annealing temperature is 710 ℃, the annealing time is 60 min, rapid annealing, with LNO conductive oxide as the bottom electrode, BNT ferroelectric thin film comprehensive performance is better. Under the condition, the residual polarization Pr value is about 30.05μC/cm2, coercive field is about 103kV/cm. After more than 108 times in turn, the residual polarization value Pr to fall by about 9%. When the voltage is low, the BNT/LNO is ohmic contact interface, the interface is schottky barrier.When under the condition of high voltage, the main leakage current mode is current limitation for the space, the main reason is using LNO as electrode. The polarization remaining value of BNT/LNO/Si thin film is bigger than BNT/Pt/Si films, the anti-fatigue performance is also better than with Pt as the bottom electrode, but the leakage current density is bigger. This basically is the introduction of LNO electrodes having the effect of buffer layer, so it can reduce the the presence of oxygen vacancy in BNT thin film, but also increases the defects,.(3) Different Ni content on BNT ferroelectric thin film is studied to analyse the influence of crystal structure, surface morphology, electrical hysteresis loop, the leakage current, and the fatigue performance. It is found from the experimental results, when the doping amount is x= 0.2, the ferroelectric thin film comprehensive performance is the best. Residual polarization value by not doped 39.1 μC/cm2 changes to 64.2 μC/cm2, leakage current density is10-7 orders of magnitude down to about 10-9 orders of magnitude. This suggests that the right amount of Ni doping, can improve the electric properties of BNT ferroelectric thin films, making BNT ferroelectric thin film to meet the requirements of the applied in high-performance ferroelectric memory. |
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