Study on the finite-size effects in ferroelectric thin films and fine-particles

铁电薄膜和细颗粒的有限尺寸效应研究

基本信息

批准号：
09450126
负责人：
ISHIKAWA Kenji
金额：
$ 2.11万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450126/
关键词：
ferroelectrics thin film fine-particle finite size effect surface relaxation PbTiOィイD23ィエD2 BaTiOィイD23ィエD2 low temperature growth 相転移 PZT レーザアブレーション

项目摘要

Finite size effects on the dielectric properties in ferroelectric materials were studied. Recently, the thickness of ferroelectric films is less than several tens of nanometer. Accordingly, the diameter of the particles in the film may be less than 10 nm. It is known that some dielectric properties differ from that of bulk materials when the size of crystallites approaches nano-meter size. However, the microscopic understanding of the size effect has not been obtained. In this research, we deal with the size effects on the phase transition in several perovskite type ferroelectrics.The first result concerns with the origin of the size effect on the phase transition. The size effects are successfully described by phenomenological theories based on the Landau-Ginzburg equation. The theory assumes the electric polarization near the surface is not uniform and differs from the bulk value. We found that the crystal lattices of lead titanate and barium titanate relaxes towards outside by X-ray measurements with the use of a simple model. We pointed out that the size effect should be caused by the non-homogenous polarization caused by the surface relaxation.We also studied the low-temperature growth of perovskite type ferroelectric films. If we can crystallize the film at low temperatures, we can obtain film composed of very small particles. The phase transition temperatures of such small particle should be lower than that of bulk crystals by the size effect. The dielectric constant of the film is expected to be larger than that of bulk material. We proposed a technique to insert a seeding layer between the film and the substrate. For example, insertion of PbTiOィイD23ィエD2 seeding layer made it possible to obtain a well crystallized film at very low temperature such as 450℃.

对铁电材料中饮食特性的有限尺寸影响是研究的。最近，铁电膜的厚度小于几十纳米。据此，膜中颗粒的直径可能小于10 nm。众所周知，当微晶的大小接近纳米米大小时，某些与大量材料不同的营养特性不同。但是，尚未获得对尺寸效应的微观理解。在这项研究中，我们处理了几种钙钛矿类型铁电的尺寸对相变的尺寸影响。首先关注的是尺寸效应对相变的起源。基于Landau-Ginzburg方程的现象学理论成功地描述了大小效应。该理论假设表面附近的电偏振不均匀，并且与整体值不同。我们发现，使用简单的模型，通过X射线测量值的滴钛酸盐和钛酸钡的晶格放松了外部。我们指出的是，尺寸效应应是由表面弛豫引起的非基础极化引起的。我们还研究了钙钛矿型铁电膜的低温生长。如果我们可以在低温下将膜结晶，我们可以获得由很小的颗粒组成的膜。通过尺寸效应，这种小粒子的相变温度应低于散装晶体的温度。预计膜的顽固常数将大于散装材料。我们提出了一种技术，以在膜和底物之间插入一个播种层。例如，PBTIOI D23E D2播种层的插入使得在非常低温（例如450℃）上获得结晶薄膜成为可能。