溶胶凝胶法制备镁掺杂钛酸锶铅和银掺杂锆钛酸铅薄膜及其介电性能研究

发布时间：2018-03-16 09:55

本文选题：渗流效应　切入点：铁电薄膜　出处：《浙江大学》2016年博士论文　论文类型：学位论文

【摘要】：钙钛矿相铁电薄膜具有优异的铁电、介电、介电可调和光学等性能,在随机存储器、介电元器件、可调器件和光学元器件中具有广泛的应用市场和前景。本文以典型的A位和B位掺杂PbTiO_3 (PT)的(Pb,Sr)TiO_3 (PST)和Pb(Zr,Ti)O_3 (PZT)薄膜为研究对象,通过分析掺杂、取向和形成渗流型结构等手段对薄膜形成和性能的影响,探索薄膜性能改善的机理。具体研究内容及主要结论如下：1)通过溶胶凝胶法制备Mg掺杂的Pb_(0.35)Sr_(0.65)TiO_3薄膜,将Mg离子引入PST薄膜中进行B位掺杂取代Ti形成Mg"π缺陷,通过使得Ti4+变价为Ti3+形成Ti'Ti缺陷,有效地降低了薄膜内氧空位的含量,同时,薄膜体系中的Ti'Ti缺陷还可以与氧空位形成Ti'Ti～V(?)缺陷偶极子对,对氧空位的自由迁移形成有效的束缚,大大降低了氧空位的迁移能力,从而降低了薄膜的介电损耗。当Mg掺杂含量为6mo1%时,PST薄膜的介电损耗与纯PST薄膜相比降低了30%。2)利用溶胶凝胶法制备Ag掺杂的PbZr_(0.52)Ti_(0.48)O_3薄膜,通过引入过量的银离子,其中一部分掺杂进入PZT晶格从而降低由于铅挥发形成的缺陷,提高了薄膜的结晶性能。利用银铅二元共晶体系的特性,控制另一部分银离子与铅离子在热处理前期形成了Ag-Pb合金亚稳过渡相，，并在随后的热处理过程逐渐分解形成了纳米银颗粒,解决了PZT薄膜结晶能力弱而难以在其中形成纳米银的问题,并形成了掺杂Ag/PZT薄膜的渗流结构体系,薄膜的介电常数有了显著的提高,渗流型Ag/PZT薄膜的介电常数比纯PZT的介电常数高出230%。同时,薄膜中纳米银增强了薄膜内部电场,降低了薄膜高介电可调性和铁电性所需的调制电压。在获得相同性能的情况下,渗流型Ag/PZT薄膜的的介电可调调制电压和矫顽场比纯PZT薄膜的分别低45%和29%。3)在取向PT的基板上制备取向PZT的过程中,在体系中引入银离子,由于在取向PT上诱导取向PZT形成时,PZT的结晶能低,能迅速结晶形成致密的基体,对Ag的扩散形成强的阻碍作用,降低了Ag的扩散速率,从而在取向PZT中形成了纳米银颗粒,在取向PZT中实现了渗流效应,大大提高了薄膜的介电可调性能和降低了调制电压,与随机取向的纯PZT相比,取向PZT复合纳米银薄膜的介电可调性高出100%,调制电压低60%。4)利用纳米银的等离子共振吸收峰的峰位与其粒径有关,设计在薄膜中形成一定粒径分布的纳米银,从而提高了薄膜光的吸收宽度。通过控制溶胶形成以及热处理,在薄膜中形成了平均尺寸为30nnm的六方银和平均尺寸为5nnm的立方银,产生了相互不重叠的吸收峰,将光的吸收宽度提高了35%。
[Abstract]:Perovskite ferroelectric thin films have excellent ferroelectric, dielectric, dielectric and harmonic optical properties, in random access memory, dielectric components, Tunable devices and optical components have a wide range of applications and prospects. In this paper, the typical PbTiO_3 doped PbTiO_3 thin films with A and B sites are studied, and the PbZrTiO3 PZT3 thin films are studied. The effects of orientation and formation of percolation structure on the formation and properties of Pb_(0.35)Sr_(0.65)TiO_3 thin films were investigated. The main conclusions are as follows: 1) Mg-doped Pb_(0.35)Sr_(0.65)TiO_3 thin films were prepared by sol-gel method. Mg ~ (2 +) was introduced into PST film to replace Ti with B site doping to form mg "蟺 defect. By changing the value of Ti4 to Ti3 to form Ti'Ti defect, the content of oxygen vacancy in the film was reduced effectively, at the same time, the content of oxygen vacancy in the film was reduced. The Ti'Ti defects in the thin film system can also be formed with the oxygen vacancy. The defect dipole pair forms an effective binding on the free migration of oxygen vacancies, which greatly reduces the migration capacity of oxygen vacancies. Therefore, the dielectric loss of PST thin films was reduced by 30. 2 when mg doping content was 6 mol / 1%. Ag-doped PbZr_(0.52)Ti_(0.48)O_3 thin films were prepared by sol-gel method, and excessive silver ions were introduced into the films. Some of them are doped into the PZT lattice to reduce the defects due to lead volatilization and improve the crystalline properties of the films. The metastable transition phase of Ag-Pb alloy was formed by controlling the other part of silver ion and lead ion in the early stage of heat treatment, and the silver nanoparticles were gradually decomposed during the subsequent heat treatment. It solves the problem that the crystalline ability of PZT thin films is weak and it is difficult to form nanocrystalline silver in the films, and the percolation structure system of doped Ag/PZT thin films is formed. The dielectric constant of the films has been greatly improved. The permittivity of percolation type Ag/PZT film is 230% higher than that of pure PZT. At the same time, silver nanoparticles in the film enhance the internal electric field of the film and reduce the modulation voltage required for the high dielectric tunability and ferroelectricity of the film. The dielectric tunable modulation voltage and coercive field of percolated Ag/PZT thin films are 45% and 29.3 lower than those of pure PZT thin films, respectively. Silver ions are introduced into the system during the preparation of oriented PZT on the substrate of oriented PT. Due to the low crystallization energy of PZT induced by orientation PT and the rapid crystallization to form a dense matrix, the diffusion of Ag is strongly hindered, and the diffusion rate of Ag is decreased, thus the silver nanoparticles are formed in the oriented PZT. The percolation effect is realized in the oriented PZT, which greatly improves the dielectric tunability of the films and reduces the modulation voltage. Compared with the randomly oriented pure PZT, the percolation effect is achieved. The dielectric tunability of oriented PZT composite silver nanofilms is higher than 100 and the modulation voltage is lower than 60.4) the peak position of plasmon resonance absorption peak of silver nanoparticles is related to its particle size, and a certain size distribution of silver nanocrystalline silver is designed in the films. By controlling the formation of sols and heat treatment, hexagonal silver with an average size of 30 nm and cubic silver with an average size of 5 nm were formed in the films, resulting in non-overlapping absorption peaks. The absorption width of light is increased by 35%.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TB383.2

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