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锆钛酸钡钙铁电薄膜的制备及光学性能研究
王红光
Subtype硕士
Thesis Advisor徐金宝
2015-05-24
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline材料物理与化学
Keyword铁电薄膜 椭圆偏振光谱仪 吸收系数 铁电畴
Abstract

随着微电子学、集成光学、自旋电子器件等领域的迅速发展,电子器件小型化、轻量化、集成化的要求使得薄膜材料在人们的日常生活中扮演着越来越重要的地位。铁电薄膜材料因其特殊的介电性、压电性、热释电性、铁电性等特性和相互之间的耦合功能使其在制作声表面波器件、红外热释电探测器、光波导、铁电随机存储器等多种器件上有着重要的应用。铁电薄膜的研究已经发展成为高新技术领域的前沿和热点之一。具有ABO3钙钛矿结构的BaTiO3基材料体系是铁电薄膜领域研究的重要体系之一,优异的介电、压电、热释电性能,以及无污染的优点使其获得了极大的关注。其中,0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3(BCZT)材料由于准同型相界(MPB)的存在而具有出色的压电性、热释电性等特性,对其力学、电学、光学等方面的性能的研究吸引着研究者的目光。针对锆钛酸钡钙铁电薄膜在电光器件、红外探测器等光学领域的广阔应用前景和其光学性质研究不足的现状,本论文的研究集中在其光学性质的表征和分析。椭圆偏振测量术由于其极高的测量精度、便捷的测量方式和对样品无破坏的特点,在薄膜的研究领域具有不可替代的重要作用,也一直是表征薄膜厚度和光学性质的重要手段。在本文中我们通过溶胶凝胶法制备了锆钛酸钡钙铁电薄膜材料,分析了材料的结构、形貌、介电和铁电性质,使用椭圆偏振测量术详细解析了薄膜材料在不同光区和不同条件下的光学性质的变化规律。本文的研究内容主要从以下几点展开:(1)采用溶胶-凝胶制备工艺,以乙酸盐为原材料,乙酸和乙二醇甲醚为溶剂,乙酰丙酮为螯合剂,制备了锆钛酸钡钙材料的溶胶,然后在Pt/Ti/SiO2/Si衬底上制备了该材料的铁电薄膜。在950℃的退火温度下,制得的薄膜材料是四方钙钛矿结构的铁电体,室温下具有铁电性。使用椭圆偏振光谱仪测试了该薄膜材料在280 nm到850 nm范围内的光学参数,通过建立三层的光学模型和结合Tauc-Lorentz振子公式计算拟合得到材料的光学性质。结果表明,薄膜材料在632.8 nm处的折射率为2.15。其光带隙为4.18 eV,使该薄膜材料在可见光区具有较宽的光谱透射范围。(2) 使用椭圆偏振光谱仪测试了锆钛酸钡钙薄膜材料在-65℃到70℃之间的不同温度场内的光学参数,通过数据的拟合最终得到材料在不同温度下的光学性能。结果表明,薄膜材料的折射率随着温度的上升有一个先增后减的过程,在30℃左右出现一个峰值,对应于材料铁电顺电转变温度点。(3) 使用红外椭圆偏振光谱仪测得锆钛酸钡钙薄膜材料在中红外光区(2.5-12.5μm)的椭偏参数。然后通过逐层拟合,最终使用三层的光学模型和结合Brendel 振子公式计算拟合出锆钛酸钡钙薄膜材料在中红外光区的光学性质。结果表明,该薄膜材料在中红外光区具有较强的光吸收能力,在红外热释电探测领域具有很好的应用前景。

Other Abstract

With the development of microelectronics, integrated optics, spintronic devices, thin film materials play an increasingly important role in our daily life due to the requirement of miniaturization, lightweight, integration for electronic devices. The special dielectric, piezoelectric, ferroelectric properties and the coupling between them promote its significant application in electronic cells, such as surface acoustic wave device, infrared pyroelectric detector, optical waveguide, ferroelectric random access memory and so on. The research about ferroelectric thin film has become one of the front edge and hot spot of advanced technique field. The perovskite BaTiO3-based material, which has excellent electrical properties and pollution-free characteristics, is one important material system among ferroelectric thin films. The 0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 material has outstanding piezoelectric and pyroelectric properties on account of the existence of morphotropic phase boundary (MPB). Its investigation in mechanics, electricity, and optics attracts researchers’ attention. Considering the wide application prospect of BCZT thin film in the optical application like electro-optic devices and infrared detectors and its research insufficient, our research is focused on the characterization and analysis of its optical properties. Spectroscopic Ellipsometry (SE) is a powerful technique for observing the thickness and optical properties of thin films. Its advantages, like high accuracy, easy operation and non-destructive, support its irreplaceable position in thin film characterization. In this paper, we prepared BCZT thin films by Sol-gel method and surveyed its microstructure, dielectric, and ferroelectric properties. Their optical properties in different spectral range and measurement condition were interpreted detailedly by SE. The main research contents of this article are from the following points: With acetate as raw material, acetic acid and ethylene glycol methyl ether as solvent and acetylacetone as chelating agents, we prepared the BCZT collosol, and then we deposited the corresponding ferroelectric thin films on Pt/Ti/SiO2/Si substrate. By sintering it at the temperature of 950 °C, the tetragonal perovskite ferroelectric thin films can be obtained. The optical parameters of BCZT thin films from 280 nm to 850 nm were measured by SE and simulated by a three layer model and a Tauc-Lorentz oscillator formula. It turned out that: The refractive index of the thin films at 632.8 nm is 2.15; its energy band gap is 4.18 eV. The BCZT thin films have a wide spectral transmission range in visible region. The optical parameters of BCZT thin films in the temperature range from -65 °C to 70 °C were measured by SE. Its optical properties in different temperature can be gained through fitting process. Consequently, with the increment of temperature, the refractive index increases at first and then decreases. A peak lies at the temperature of 30 °C, corresponding to the ferroelectric-to-paraelectric phase transition temperature The infrared ellipsometry parameters of BCZT thin films were measured by infrared spectroscopic ellipsometry (IRSE) in mid-infrared range. By fitting data layer by layer, its optical properties were obtained with a three layer model and Brendel oscillator model. BCZT thin films have a strong light absorption in mid-infrared region, indicating its promising application in infrared pyroelectric detection.

Document Type学位论文
Identifierhttp://ir.xjipc.cas.cn/handle/365002/4263
Collection材料物理与化学研究室
Affiliation中国科学院新疆理化技术研究所
Recommended Citation
GB/T 7714
王红光. 锆钛酸钡钙铁电薄膜的制备及光学性能研究[D]. 北京. 中国科学院大学,2015.
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