Preparation And Electrical Properties Of Pb(Zr₄₀Ti₆₀)O₃ Thin Films In Microwave Magnetic Field

The oxide ferroelectric thin films,represented by(Pb(Zr_xTi_1-x)O₃,PZT),are widely used in the fields of ferroelectric memory,film capacitors and micro-electromechanical systems due to their comprehensively excellent performance.The electrical properties of the thin films are the key components that directly affect the service life of the devices.Microwave annealing is one of the appealing ways that can be used to efficiently prepare PZT ferroelectric thin films with excellent properties.To realize a better use of microwave in the preparation of the functional thin film,the heating behavior of conductive substrate in the microwave magnetic field was studied,and the interaction between microwave and materials was discussed.In addition,amorphous PZT films were prepared by the sol-gel method,and the crystallization of the thin films was achieved by microwave annealing.The effects of microwave annealing on the microstructure and electrical properties of PZT ferroelectric films were studied.Specific research contents and results are as follows:（1）By studying the heating behavior of Nb-doped SrTiO₃substrates with different Nb doping amounts（Nb:SrTiO₃:0 wt%～0.7 wt%Nb）and Si substrates with different resistivity in a microwave magnetic field,the interaction between microwave and materials was discussed.The results show that the heating behavior of Nb:SrTiO₃substrates and Si substrates mainly depend on their conductivity,skin depth and thickness.With the increase of the Nb doping concentration,the heating temperature and heating rate of the substrate in the microwave magnetic field decreased gradually.Affected by the skin depth,the substrate with the Nb doping concentration of 0.05 wt%had the best heating effect.The P-type Si substrate with resistivity of 0.05-0.1Ω·cm has the best heating behavior in a microwave magnetic field.（2）Amorphous Pb(Zr₄₀Ti₆₀)O₃thin films were deposited on Nb:SrTiO₃substrates with different Nb doping concentrations and Si substrates with different resistivity by sol-gel method.The effects of microwave annealing on microstructure and electrical properties of PZT thin films were investigated.The results show that microwave power directly acts with charged ions in the material to reduce the internal defects of PZT films,and the effect becomes more obvious with the increase of microwave power.Microwave annealing not only realizes the crystallization of the perovskite phase in a short period of time but also improves the electrical properties of PZT films.（3）Pb(Zr₄₀Ti₆₀)O₃thin films were prepared on Nb:SrTiO₃substrates with 0.7wt%Nb doping concentration by sol-gel method,crystalized the thin films by microwave annealing and conventional annealing to investigate the effects of microwave annealing on the distribution of oxygen vacancy,the width of the depletion layer and the electrical properties at the PZT/Nb:SrTiO₃interface.The results show that the residual polarization and saturation polarization of the PZT film by conventional annealing is 72μC/cm²and 86μC/cm²,while that of PZT film crystalized by microwave annealing is 78μC/cm²and 93μC/cm²,respectively.Moreover,PZT film crystalized by conventional annealing illustrates an apparent imprinting effect,whose electric field offset is 133 kV/cm,that of the PZT film crystalized by microwave annealing is 126 kV/cm,which exhibits a more symmetrical hysteresis loop.As the result of the analysis of the leakage current mechanism of the PZT/Nb:SrTiO₃interface based on the Schottky-Simmons,microwave annealing promotes the aggregation of oxygen vacancies at the PZT/Nb:SrTiO₃interface,reduces the barrier of the interface,and shrinks the width of the depletion layer.Thus,the binding of ferroelectric domains at the PZT/Nb:SrTiO₃interface is reduced,and further improving the electrical properties of PZT films.