| Due to outstanding dielectric, ferroelectric, pyroelectric properties, dielectric thin films have a great application prospect in mobile communications, satellite systems, radar and other electronic systems. But electronic devices with different functions have different requirements about the materials, only a kind of material is hard to meet the requirements in the practical application. Such as the Pb(Zr0.52Ti0.48)O3 thin films have excellent piezoelectric and ferroelectric properties, but its dielectric loss and leakage current is large, which can lead to ferroelectric memory failure; Ba(Mg1/3Ta2/3)O3 thin films have excellent microwave dielectric properties, but its dielectric constant is small, which cannot satisfies the requirement of increasing miniaturization microwave devices, to some extent,it limits the application of PZT thin film and BMTa film. In order to improve materials' combined properties to meet the application requirements of different electronic devices, people often composite two or more different kinds of materials to improve the performances.In this paper, sol-gel method and aqueous gel method is employed to prepare PZT and BMTa thin films. The effects of annealing temperature and coating layer on PZT and BMTa thin films are studied. Studies have shown that neither the annealing temperature is too high nor too low can promote the nucleation and growth of the thin films' grains. When the annealing temperature is 750 ? and the coating layers are 9, can get PZT thin films with dense microstructure, well growth grains, uniform size and less holes, at the same time we could get the relatively good performance: under the frequency of 100 kHz, the dielectric constant epsilon ?r=1600.7, dielectric loss tan?=0.098; under the 15 V applied electric field, 2Pr=56.76?C/cm2, 2Ec=105.30 kV/cm. The BMTa thin films have dense surface, and the coating layers have little influence on its microstructure and dielectric properties, under the 100 kHz, the dielectric constant is about 19, dielectric loss is about 0.025.Two kinds of structure of the BMTa/PZT composite thin films(P/B type and B/P type) are designed and pepared, the research have shown that introduce BMTa thin films can promote PZT thin film grains grow up, reduce its dielectric permittivity, dielectric loss and leakage current. Under the applied voltage of 2 V, compared to PZT thin films,the P/B composite thin films with 4 BMTa thin film layers, its leakage current down from 4.43×10-6 A/cm2 to 5.45×10-7 A/cm2, which reduced about one order of magnitude, With the increase of thickness of BMTa film, the residual polarization and coercive field of the P/B composite thin films are improved. The type of B/P composite thin films have hign dielectric constant and low dielectric loss. When the thickness of the PZT thin films is about 400 nm, the thickness of BMTa thin films is about 345 nm, B/P composite thin films' dielectric constant epsilon ?r=44.5, dielectric loss tan?=0.029, compared with the homogeneous BMTa thin films, without any increase in dielectric loss, the dielectric constant of the B/P composite thin films increased significantly, So we can regulate the dielectric constant of B/P composite thin films by changing the thickness of PZT thin films. |
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