摘 要

PZT薄膜具有较高介电常数和剩余极化强度的同时，存在介电损耗大、疲劳特性差和温度稳定性差的缺点，而BMT薄膜具有低介电损耗tan δ、高品质因数Q以及优异的频率稳定性，因此，将二者进行复合可以获得适中介电常数、低介电损耗、介电可调性良好的异质叠层薄膜，适用于移相器领域。本论文采用水溶液凝胶法制备长期澄清稳定的BMT前驱体溶液，Sol-gel法制备PZT前驱体溶液，在Pt/Ti/SiO₂/Si(100)基底上通过液相旋涂法沉积不同结构的异质叠层薄膜（其中，BP型表示重复单元中PZT层作底层，PB型表示重复单元中BMT层作底层）。探讨界面及单元层厚对BMT/PZT异质叠层薄膜微结构以及电学性能的影响规律。本文的主要研究内容及结果如下：

（1）界面个数明显影响着BMT/PZT复合薄膜的电学性能。当界面个数增多时，促进了BP型和PB型复合薄膜的钙钛矿相的生长，同时能够增大薄膜晶粒尺寸、降低孔隙率。随着异质界面个数的增多，BP型和PB型复合薄膜的介电常数增大，介电损耗减小，在1 MHz频率下，BP型的介电常数由236增加到359，介电损耗由0.2335降低到0.1013；PB型的介电常数由180增加到242，介电损耗由0.0887降低到0.0464。介电常数增强现象可以通过建立模拟等效电路图来解释，介电损耗的降低是由于界面个数的增多降低了薄膜的表面粗糙度，从而改善了薄膜的介电损耗。实验研究表明，异质界面个数可以改善BP型和PB型复合薄膜的介电可调性和品质因数，BP型的介电可调率由3.96%增加到16.46%，品质因数由0.17增加到1.62；PB型的介电可调率由6.29%增加到14.24%，品质因数由0.71增加到3.07。界面个数的增多可以提高BP型和PB型的剩余极化强度和矫顽场，这是因为界面个数增多的同时降低了单元层厚度，单元层厚度越薄，单元层之间的协同效应越强，复合薄膜中累积的应力越大，从而增大了薄膜的铁电性能。

（2）PZT层和BMT层的叠层顺序也影响着BMT/PZT异质叠层薄膜的电学性能。当复合薄膜具有相同异质界面个数时，BP型的介电常数总是高于PB型，异质界面个数为7时，BP型的介电常数为359，而PB型的只有242。异质界面个数相同时，PB型的介电损耗明显低于BP型，异质界面个数为7时，PB型的介电损耗为0.0464，而BP型的为0.1013，这是因为重复单元中BMT作底层时抑制了电子的扩散，从而降低了损耗。

关键词：PZT薄膜；BMT薄膜；异质界面；溶胶凝胶法；水溶液凝胶法

Abstract

PZT thin films have high dielectric constant and remnant polarization values, and there are shortcomings like large dielectric loss, poor fatigue property and poor temperature stability. BMT thin films have high quality factor Q, low dielectric loss tanδ and good frequency temperature stability. Therefore, BMT and PZT composite can obtain the heterogeneous composite thin film, which possess moderate dielectric constant, low dielectric loss, and high tunability, and it is suitable for the field of phase shifters. In this paper, PZT precursor solution and BMT precursor solution were prepared by sol-gel method and Water-Gel method respectively, and BMT/PZT heterogeneous composite thin films were prepared on Pt/Ti/SiO₂/Si substrate by spin coating. The effects of interfaces and unit layer thickness on the microstructure and electric properties of BMT/PZT heterogeneous composite thin films were investigated. The main contents and results of this paper are as follows:

(1) The number of interfaces significantly affected the electrical properties of BMT/PZT composite films. When the number of interfaces increases, BP type and PB type composite films have better crystallinity, and increase the grain size of the film, reduce the porosity. With the increase of the number of interfaces, the dielectric constant of BP and PB composite films increases and the dielectric loss decreases. At 1MHz, the dielectric constant of BP type increases from 236 to 359, and the dielectric loss decreases from 0.2335 to 0.1013. The dielectric constant of the PB type increases from 180 to 242, and the dielectric loss decreases from 0.0887 to 0.0464. The dielectric constant enhancement can be explained by the Maxwell-Wagner effect, and the dielectric loss is reduced due to the number of interfaces increasing the surface roughness of the film. With the increase of the number of interfaces, the dielectric tunability rate and the quality factor of the BP type and PB type composite films increased. The dielectric tunability rate of BP type increased from 3.96% to 16.46%, and the quality factor from 0.17 to 1.62. The dielectric tunability rate of the PB type increased from 6.29% to 14.24%, and the quality factor increased from 0.71 to 3.07. The remnant polarization and coercive field of BP type and PB type composite films increase with the increase of the number of interfaces, which is due to the increase of the number of interfaces. When the number of interfaces is increasing, the thickness of the unit layer would be thinner. The stronger the synergistic effect, the greater the accumulated stress in the composite film, which led to increasing the ferroelectric properties of the composite film.

(2) The stacking order of PZT layer and BMT layer also affected the electrical properties of BMT/PZT heterogeneous composite thin films. When composite films have the same number of heterogeneous interfaces, the dielectric constant of the BP type is always higher than that of the PB type. When the number of heterogeneous interfaces is 7, the dielectric constant of the BP type is 359 and the PB type is only 242. When the number of heterogeneous interfaces is the same, the dielectric loss of PB type is obviously lower than that of BP type. When the number of heterogeneous interface is 7, the dielectric loss of PB type is 0.0464 and the BP type is 0.1013. Because in the repeating unit, BMT is in the bottom and BMT film hinders the diffusion of electrons, which reduce the loss.

Key Words：PZT; BMT; Sol-Gel method; Water-Gel method; Interface

目 录

摘 要 I

Abstract II

第1章 绪论 1

1.1 PZT铁电薄膜材料 1

1.2 BMT介电薄膜材料 2

1.3 异质叠层薄膜 3

1.4 介质薄膜的制备方法 4

1.5 本论文研究的目的意义及研究内容 5

第2章 实验方法 6

2.1 设备与原料 6

2.2 前驱体溶液的制备 7

2.2.1 PZT前驱体溶液的制备 7

2.2.2 BMT前驱体溶液的制备 8

2.3 薄膜的制备 9

2.3.1 基片清洗 9

2.3.2 PZT薄膜的制备 10

2.3.3 BMT薄膜的制备 11

2.3.4 BMT/PZT、PZT/BMT异质叠层薄膜的制备 11

2.4 结构与性能表征方法 12

2.4.1薄膜的结构表征技术 12

2.4.2薄膜的电学性能表征技术 12

第3章 结果与讨论 14

3.1 界面个数对BMT/PZT复合薄膜性能的影响 14

3.1.1 BMT/PZT复合薄膜的X射线衍射分析 14

3.1.2 BMT/PZT复合薄膜的场发射扫描电镜分析 14

3.1.3 BMT/PZT复合薄膜的介电性能分析 15

3.1.4 BMT/PZT复合薄膜的介电可调性分析 16

3.1.5 BMT/PZT复合薄膜的铁电性能分析 17

3.2 界面个数对PZT/BMT复合薄膜性能的影响 18

3.2.1 PZT/BMT复合薄膜的X射线衍射分析 18

3.2.2 PZT/BMT复合薄膜的介电性能分析 18

3.2.3 PZT/BMT复合薄膜的介电可调性分析 20

3.2.4 PZT/BMT复合薄膜的铁电性能分析 21