钇锰交替掺杂钛酸锶钡薄膜预热处理研究

发布时间：2018-05-25 05:08

  本文选题：交替掺杂 + 钛酸锶钡薄膜　； 参考：《电子科技大学》2015年硕士论文

【摘要】：BST铁电薄膜因其具有良好的铁电、介电、压电等方面的特性,成为近年来研究的一个热点。其优良的性能可以使其应用在移相器、动态随机存储器等微波调谐器件当中。然而,应用在微波调谐领域要求BST薄膜必须同时具有高的调谐率和低的介电损耗。纯的BST虽然可以达到较高的调谐率,但是介电损耗较高阻碍了其应用。为了克服这一缺点,本研究团队前期进行了大量的研究,包括改进薄膜的制备工艺、进行单一掺杂、复合掺杂以及交替掺杂来提高薄膜的综合介电性能,都取得了良好的进展。尤其是钇(Y)和锰(Mn)交替掺杂对于提高薄膜的综合介电性能有着良好的促进作用。本团队在研究中发现,在制备薄膜的过程中加入预热处理过程可以大大的改善薄膜的性能,目前关于这方面的研究还比较欠缺。因此,本论文在前期研究的基础上,重点研究不同的预热处理方式以及不同的掺杂浓度组合对钇(Y)和锰(Mn)交替掺杂薄膜的介电性能的影响,并深入地分析了其机理。利用XRD、SEM以及HP4294A阻抗分析仪测试了薄膜的相结构、表面形貌及介电性能,取得了以下创新性成果:1、适当的预热处理可以有效地提高薄膜的综合介电性能,不仅使薄膜保持较高的调谐率,且可以有效地降低介电损耗。其中,在600℃条件下进行预热处理,保持Y的掺杂浓度为1%不变,随着Mn的掺杂浓度从2%升到5%,薄膜的介电损耗经历了先减小后增大的过程,当Mn的掺杂浓度为3%时,薄膜的调谐率为47.90%,最大介电损耗低至1.98%;在650℃条件下进行预热处理,薄膜性能有所提高,3mol%Mn/1mol%Y薄膜的最大介电损耗降低至1.38%,调谐率为48.2%。2、对薄膜的预热处理温度进行进一步优化,在550℃条件下进行预热处理,获得了较其他单一温度预热处理更低的介电损耗,随着Mn的浓度从2%升到5%,薄膜的最低介电损耗分别为0.79%、0.97%、0.92%,均在1%以下。并且在降低了损耗的基础上,保持了较高的调谐率,三种浓度下薄膜的调谐率依次为56%、56%、48.6%,表现出优异的介电性能。3、在单一温度预热处理方式的基础上,提出了一种新型的预热处理方式:梯度预热处理。随着薄膜层数的增加,薄膜的预热处理温度呈现梯度的变化,由第一层的550℃逐渐升高到了第六层的650℃。在此预热处理方式下,随着Mn掺杂浓度的增大,薄膜的晶化逐渐增强,晶粒尺寸逐渐增大。薄膜的综合介电性也能得到了大幅度的提升,保持Y的掺杂浓度不变,当Mn的掺杂浓度为2%时,薄膜的最大损耗和最低损耗分别为1.4%和0.49%,同时对应高达50.2%的调谐率;当Mn的掺杂浓度为3%时,薄膜的最高损耗和最低损耗分别为1.3%和0.404%;随着Mn的浓度的进一步的升高,介电损耗有所升高,但是仍然保持在较低的水平,当Mn的浓度为6%时,最高损耗和最低损耗分别为1.33%和0.635%。SEM测试结果也表明:经过梯度预热处理的薄膜表面形貌良好,晶粒细小均匀,孔隙更少。
[Abstract]:BST ferroelectric thin films have become a hot research area in recent years because of their good ferroelectric, dielectric and piezoelectric properties. It can be used in microwave tuners such as phase shifters, dynamic random access memory (DRAM) and so on. However, in the field of microwave tuning, BST films must have high tuning rate and low dielectric loss. Although pure BST can achieve high tuning rate, high dielectric loss hinders its application. In order to overcome this shortcoming, the research team has done a lot of research, including improving the preparation process of thin films, single doping, composite doping and alternating doping to improve the comprehensive dielectric properties of the films, and has made good progress. In particular, the alternating doping of yttrium and manganin) has a good effect on improving the comprehensive dielectric properties of the films. The team found that the performance of the films can be greatly improved by adding preheating process in the process of preparing the films, but the current research on this aspect is still relatively lacking. Therefore, on the basis of previous studies, this paper focuses on the effects of different preheating methods and different doping concentration combinations on the dielectric properties of YY) and MnMnMn) alternate doped films, and the mechanism of them is analyzed in depth. The phase structure, surface morphology and dielectric properties of the films were measured by XRD-SEM and HP4294A impedance analyzer. The following innovative results were obtained: 1. Proper preheating treatment can effectively improve the comprehensive dielectric properties of the films. The film can not only keep a high tuning rate, but also reduce the dielectric loss effectively. The dielectric loss of the films decreases first and then increases with the increase of mn doping concentration from 2% to 5%. When mn doping concentration is 3%, the dielectric loss of the films decreases and then increases. The tunable rate of the film is 47.90, and the maximum dielectric loss is as low as 1.98. When the film is pretreated at 650 鈩，

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