权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Time resolved and in-situ structural analysis of a ferroelectric thin film during polarization switching using synchrotron-based diffraction

使用同步加速器衍射对铁电薄膜偏振切换过程中的时间分辨和原位结构进行分析

基本信息

批准号：
18310085
负责人：
SAKATA Osami
金额：
$ 8.31万
依托单位：
Japan Synchrotron Radiation Research Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

A synchrotron-based time-resolved diffraction method has been developed for characterizing a piezoelectric thin film. This was why we needed to complete a time-resolved diffraction system equipped with a ferroelectric test system. We introduced the fenoelectric test system(Toyotechinca FCE-HS100D) for high-speed characterization of polarization in a ferroelectric thin film and modified it for a time-resolved and in-situ measurement. We have succeeded in detection of electrostuction(electuc-field-induced strain) of ferroelectric thin films such as epitaxial Pb(Zr_<0.25>, Ti_<0.75>) O_3(PZT) and polycrystalline BiFeO_3(BFO) films. The electrostnctive strain was induced by an applied electric field having repeated ns-width pulses. In addition, we determined piezoelectric constants from diffraction peak shifts.The apparatus receives a pulse pattern formed by a 508 MHz counter using the RF signals as a clock of the Spring-8 storage ring and applies a pulse electric field to a sample. We use … More d the pulse pattern as a trigger ; accordingly the applied electric fields were synchronized with incident x-rays.A sample was a 750 nm-thick PZT film epitaxially grown on a SrRuO_3 thin film using metal organic chemical vapor deposition. Upper Pt electrodes with a diameter of 100 μm were arrayed in a lattice. One prober touched an upper electiode Pt incident x-rays hit, while the other touched another upper electrode. We aligned a polar direction in the PZT film using an applied voltage of 30 V in advance ; consequently, polarization(+Pr) remamed. We made a Θ-2Θ scan around the PZT 004 Bragg angle and recorded a diffraction- intensity profile as a function of time at each combination of Θ and 2Θ angle using an avalanche photo diode detector for a fixed voltage of 0, 10, 20 30 40 50, 55, 60, 70, and 75 V, respectively. The unipolar-rectangular-shape pulse width of 200 ns was repeatedly applied with a period of 800 ns. Measured time used at each angle was 100 s. An incident slit size used was 15×15μm.We observed that the 004 main peaks were shifted toward the lower angle only when the applied field was on. This indicates that the(004) lattice-plane spacing along the surface normal was lengthened because of electrostriction. The pulse electric-field induced strain Δd / d estimated from the main peak shift for 50 V was 0.0004 ; correspondingly, piezoelectric constant d_<33> was 13 pm / V. Furthermore, our finding is that the other peak appeared at a lower angle. d_<33> obtained from the other peak shift is ca. 50 pm / V. This value almost corresponds to that obtained using AFM measurements.We also applied the time-resolved diffraction method to characterizing a polycrystalline BFO thin film. The applied voltages were 0, 3, 5, 8, 10, 11, and 12 V with a 150 ns width and a 804 ns periodicity. Obtained d_<33> values for the(001) and(110) domain were 27.8 and 26.4 pm / V, respectively. Less

本文提出了一种基于同步辐射的时间分辨衍射方法来表征压电薄膜。这就是为什么我们需要完成一个配备铁电测试系统的时间分辨衍射系统。我们介绍了铁电测试系统（Toyotechinca FCE-HS 100D）的高速表征的铁电薄膜的极化，并修改它的时间分辨和原位测量。我们已成功地探测了Pb（Zr_<0.25>，Ti_<0.75>）O_3（PZT）外延薄膜和BiFeO_3（BFO）多晶薄膜的电致应变。电致应变由具有重复ns宽度脉冲的外加电场引起。该装置接收由508 MHz计数器形成的脉冲图形，将RF信号用作Spring-8储存环的时钟，并对样品施加脉冲电场。我们使用 ...更多信息采用金属有机化学气相沉积法在SrRuO_3薄膜上外延生长了750 nm厚的PZT薄膜。上部Pt电极直径为100 μm，呈点阵状排列。一个探测器接触入射X射线击中的上电极，而另一个接触另一个上电极。我们在PZT薄膜中使用预先施加的30 V的电压对准极性方向;因此，极化（+Pr）reamed。我们围绕PZT 004布拉格角进行了Θ-2Θ扫描，并使用雪崩光电二极管检测器分别在0、10、20、30、40、50、55、60、70和75 V的固定电压下记录了在Θ和2Θ角的每种组合下随时间变化的衍射强度分布。以800 ns的周期重复施加200 ns的单极矩形脉冲宽度。每个角度所用的测量时间为100 s。当入射狭缝尺寸为15×15μm时，我们观察到004主峰只有在外加电场作用下才向较低的角度移动，这表明（004）晶格面间距沿着表面法线方向由于电致伸缩而变长。由50 V时的主峰位移估算出的脉冲电场诱导应变Δd / d为0.0004，相应的压电常数d_<33>为13 pm /V。此外，我们发现另一个峰出现在较低的角度。从<33>另一个峰移获得的d_是ca。50 pm /V。这个值几乎对应于使用AFM测量得到的。我们还应用时间分辨衍射方法来表征多晶BFO薄膜。施加的电压为0、3、5、8、10、11和12 V，宽度为150 ns，周期为804 ns。得到<33>的（001）和（110）结构域的d_值分别为27.8和26.4 pm / V。少