论文总字数：22071字

摘 要

铁电材料是具有铁电性能的一类材料。近年来，铋系层状铁电薄膜如钛酸铋（Bi₄Ti₃O₁₂-BIT）等已经开始替代锆钛酸铅（PZT）在铁电存储器中被广泛地应用，因为它们具有较低的结晶温度，在多次反转之后没有明显的疲劳现象的特点。最重要的是它不含重金属所以对环境无污染。研究表明，对 BIT晶体进行A 位（Bi）、 B 位（Ti）以及 A 位/B 位共掺杂能有效提高其剩余极化并降低其矫顽场。

本文选择Nd³ /Zr⁴ 共掺杂BIT铁电薄膜作为研究内容，考察Zr⁴ 掺杂（x=0，0.05）对Bi_3.18Nd_0.85Ti_3-xZr_xO₁₂（BNTZ）铁电薄膜微结构及电学性能的影响。利用溶胶凝胶法（Sol-Gel）在 Pt/Ti/SiO₂/Si(100)衬底上制备了不同 Zr 含量（x=0，0.05）掺杂的 Bi_3.15Nd_0.85Ti_3-xZr_xO₁₂（BNTZ）铁电薄膜。利用 X-射线衍射（XRD）， 自动元件分析仪（ACA）和铁电测试仪对薄膜结构和电学性能进行测试。通过结构测试我们发现掺杂并没有改变薄膜的晶体结构，薄膜掺杂前后均表现出钙钛矿结构。电学性能测试表明薄膜同时具有较好的铁电和漏电性能。其中当 x=0.05 时，薄膜具有较大的剩余极化值（2Pr） 45.32 μC/cm² 和最小的矫顽场190 kV/cm。

关键词：钛酸铋 铁电薄膜 掺杂 溶胶-凝胶法

Study on ferroelectric properties of doped Bi₄Ti₃O₁₂ thin film

Abstract

Ferroelectric materials are a class of materials which have ferroelectric properties. Bismuth layer-structured ferroelectrics materials such as Bi₄Ti₃O₁₂ (BIT) thin films have been recognized as the promising materials in place of the conventional lead zirconate titanate (PZT) used for NvFeRAMs device due to its relatively low crystallization temperature, excellent fatigue endurance and free-pollution. Many literatures demonstrated that it’s an effcetive method to impove the remnant polarization and coercive field of BIT crystal via A-site substitution, B-site substitution and A-site/B-site co-substitution. In this paper, Nd³ /Zr⁴ co-doped BIT ferroelectric thin films were used to study the influence of different concentration of Zr⁴ on the properties of BIT ferroelectric thin films.

The effect of Zr⁴ doping (x = 0, 0.05) on the microstructure and electrical properties of Bi_3.18Nd_0.85Ti_3-xZr_xO₁₂ (BNTZ) ferroelectric thin films was investigated by using Nd³ /Zr⁴ co-doped BIT ferroelectric thin films.The Bi_3.15Nd_0.85Ti_3-xZr_xO₁₂ (BNTZ) films with Zr content (x=0, 0.05) were prepared on Pt/Ti/SiO₂/Si (100) substrates by Sol-Gel technique. The crystal structures of BNTZ films were analyzed by X-ray diffraction (XRD). The effects of Zr contents on the ferroelectric, dielectric properties, and leakage current of BNTZ films were investigated. The XRD results demonstrated that all the films possessed a polycrystalline phase bismuth-layered structure. Among these films, the film with Zr content x=0.05 held the better remanent polarization (2Pr) of 45.32 μC/cm² and a low coercive field (2Ec) of 190 kV/cm.

Key Word: bismuth titanate; ferroelectric films; substitution; Sol-Gel

目录

摘要 I

Abstract II

第一章 绪论 1

1.1 铁电材料基本概念 1

1.1.1铁电畴 1

1.1.2电滞回线 1

1.1.3 居里-外斯定律 2

1.2 铁电材料分类及结构 2

1.3 铁电薄膜简介 4

1.4 铁电薄膜制备技术 4

1.4.1射频磁控溅射法 5

1.4.2 金属有机物化学气相沉积法 5

1.4.3溶胶-凝胶法 5

1.5 国内外铁电材料研究进展 6

1.6 本论文主要研究内容 9

第二章 实验及测试方法 10

2.1实验原料及设备 10

2.1.1实验中所需原料及设备 10

2.1.2衬底的选择 10

2.2铁电薄膜的制备 12

2.2.1 BIT溶胶配置 12

2.2.2匀胶涂抹及热处理 12

2.3 材料性能表征设备 13

2.3.1 X-射线衍射（XRD） 13

2.3.3 振动样品磁强计（VSM） 14

2.3.4 铁电测试仪 14

第三章 实验结果与分析 15

3.1 BNTZ铁电薄膜结构性能 15

3.2 BNTZ铁电薄膜铁电性能 16

3.3 BNTZ铁电薄膜 C-V特性 17

3.4 BNTZ铁电薄膜介电性能 18

3.5 BNTZ铁电薄膜 E-J 特性 19

3.6 小结 21

第四章 总结与展望 22

4.1 总结 22

4.2 展望 22

参考文献 23

致谢………………………………………………………………………………………….....26

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