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

已经开发了一种基于同步加速器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配备有铁电测试系统的时间分辨衍射系统的原因。我们引入了Fenoelectric Test System（Toyotechinca FCE-HS100D），用于在铁电薄膜中高速表征对极化的表征，并将其修改以进行时间分辨和原地测量。我们已经成功地检测了铁电薄膜的静电（电场诱导的应变），例如外延PB（ZR_ <0.25>，Ti_ <0.75>）O_3（PZT）和Polycrystalline Bifeo_3（BFO）膜。通过具有重复的NS宽度脉冲的施加的电场诱导电能应变。此外，我们从衍射峰移动中确定了压电常数。该设备使用RF信号作为Spring-8存储环的时钟接收508 MHz计数器形成的脉冲图案，并将脉冲电场应用于样品。我们使用…更多的脉冲图案作为触发因素；因此，使用金属有机化学蒸气沉积的SRRUO_3薄膜，在SRRUO_3薄膜上施加了750 nm厚的PZT膜，将应用的电场与入射X射线同步。将直径为100μm的上部PT电子在晶格中排列。一个探针触及了上部选举PT事件X射线击中，而另一个触摸了另一个上层元素。我们使用30 V的施加电压在PZT膜中对齐极性。因此，重新占极化（+PR）。我们在PZT 004 BRAGG角上进行了θ-2θ扫描，并使用雪崩光二极管检测器在每种组合的每种组合下记录了衍射强度曲线，分别为0、10、20 30 30 30 50、55、60、70、70、70、70和75 V，在θ和2θ角的每种组合下进行了衍射。在800 ns的周期中，反复应用200 ns的单极矩形脉冲宽度。在每个角度使用的测量时间为100 s。所使用的入射缝尺寸为15×15μm。我们观察到，仅当施加场打开时，004主峰才向下移动。这表明（004）沿表面正常的（004）晶格平面间距由于电术而延长。脉冲电场诱导的应变ΔD / d从主峰值移位50 V估计为0.0004；相应地，压电常数d_ <33>为13 pm / v。此外，我们的发现是另一个峰出现在较低的角度。从另一个峰值移位获得的D_ <33>是Ca。 50 pm / v。该值几乎对应于使用AFM测量结果获得的值。我们还应用了时间分辨的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，具有150 ns宽度和804 NS周期性。（001）和（110）域获得的D_ <33>的值分别为27.8和26.4 pm / v。较少的