Structure And Properties Studies Of PZT/BTO Multilayer Heterogeneous Films Based On BaPbO₃ Electrode

High density and high integration electronic products require further reduction of capacitor size to improve the capacitor's specific capacitance and electrical performance.Therefore,the development of new film capacitors has become the current research hotspot of capacitor integration technology.However,when the thickness of single ferroelectric film decreases,the dielectric constant decreases,the film leakage current increases,many other indicators of the capacitor decreases.So single-layer film capacitors can no longer meet the needs of these applications.The use of multilayer heterogeneous films and their enhancement effect is a feasible solution.In this dissertation,PZT/BTO heterogeneous films with excellent ferroelectric and dielectric properties are selected as the object of study to improve the electrical properties of the films through cycle structure design and electrode system improvement.The following three main aspects of work were carried out.Pb(Zr_0.52Ti_0.48)O₃/Ba Ti O₃(PZT/BTO)multilayer heterogeneous films were prepared on Pt/Ti/Si O₂/Si substrate by sol-gel method,and the influence of different thickness ratios on the properties of the heterogeneous structures was investigated.The result shows that there exists a dielectric enhancement when the BTO layer fraction x is around 0.5,and at this fraction,the dielectric constant of PZT/BTO is 490 at 100 k Hz,which is far more than that of monolithic PZT or BTO films(375 and 181,respectively).The thermodynamic analysis shows that the measured dielectric constant is close to the simulation values.The result indicates that the internal field resulting from the polarization mismatch between two ferroelectric layers contributes to the enhancement of PZT/BTO heterogeneous thin films.The effects of different film cycle thicknesses on the properties of PZT/BTO heterogeneous films were investigated.Under the same total thickness,the roughness accumulation problem of PZT/BTO heterogeneous films is improved with the increase of the number of film layers with the thinner cycle thickness.The films can grow with better 2D surface and improve their film formation quality,and the leakage current and loss of the films are reduced.According to the Maxwell-Wagner effect,as the period thickness decreases,the space charge polarization and the displacement polarization at the interface increase the overall polarization level,resulting in a gradual increase in the dielectric constant,the?_r is 516 and the tan?is 0.082 at 100 k Hz.The optimal sputtering process for Ba Pb O₃(BPO)conductive films was investigated by magnetron sputtering.Compared with metal electrode,it was found that BPO can effectively improve the film formation quality and fatigue characteristics of ferroelectric films when it is used as the bottom electrode.As the thickness of the BPO film increases,the stress state of the PZT/BTO film changes and more c-domains are converted to a-domains,leading to a decrease in ferroelectric and fatigue behavior.At the BPO thickness of 160 nm,there is the highest residual polarization and lower coercivity field,and after 10⁸ polarization reversal,the residual polarization strength is 94.5%of the initial state,which has excellent fatigue resistance properties.