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Nondestructive evaluation of ferroelectric domain structure poled and driven by electric fields of surface electrode pairs by ultrasonic atomic force microscopy

通过超声原子力显微镜对表面电极对电场极化和驱动的铁电畴结构进行无损评估

基本信息

批准号：
17560627
负责人：
TSUJI Toshihiro
金额：
$ 2.3万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

Scanning probe microscopy has revealed an origin of a polarization fatigue and a mechanism for improving ferroelectric thin films for memory devices and MEMS actuators. An observation method with a nanoscale resolution for observing domains during the device operation has not been established. In this study, ultrasonic atomic force microscopy (UAFM) that can measure elastic property on the nanoscale was combined with narrow gap of surface electrode pairs (SEP) fabricated on ferroelectric materials in order to establish the technique for the evaluation of ferroelectric materials in practical environment during the device operation. We used lead magnesium niobate - lead titanate single crystal (Pb(Mg_<2/3>Nb_<1/3>)O_3-PbTiO_3 : PMN-PT) as a sample that shows significantly high piezoelectric coefficient by poling in the direction along certain crystal orientation. As a result, an electric field of SEP was found to drive ferroelectric domain for the first time, although the topmost surface of the sample was depolarized by heating up during the vacuum deposition of Au/Cr thin film of SEP since low Curie temperature of 130℃. Then, the domain boundary of the depolarized structure was observed by UAFM, so that it was found to be tilted under the surface by small angle with respect to the observation plane. A subsurface imaging in PMN-PT with high dielectric constant is difficult in piezoresponse force microscopy that is generally used for imaging ferroelectric domain configuration, and it was demonstrated that UAFM is useful for analyzing 3D structure of subsurface defect. In conclusions, it was verified that the application of the electric field by SEP is useful for the nondestructive evaluation of ferroelectric domain structure by UAFM. From these results, the basis of UAFM evaluation of ferrolectrics using SEP was established, so that the purpose that was originally intended was achieved.

扫描探针显微镜揭示了极化疲劳的起源以及改进存储器件和 MEMS 执行器的铁电薄膜的机制。尚未建立用于在设备运行期间观察域的纳米级分辨率的观察方法。本研究将可测量纳米尺度弹性性能的超声原子力显微镜（UAFM）与铁电材料上制作的窄间隙表面电极对（SEP）相结合，以建立在器件运行过程中实际环境中评估铁电材料的技术。我们以铌酸铅镁-钛酸铅单晶(Pb(Mg_<2/3>Nb_<1/3>)O_3-PbTiO_3:PMN-PT)为样品，通过沿一定晶向的极化，表现出显着的高压电系数。结果，尽管由于130℃的低居里温度，在真空沉积SEP的Au/Cr薄膜期间样品的最表面因加热而去极化，但首次发现SEP的电场驱动铁电畴。然后，通过UAFM观察去偏结构的磁畴边界，结果发现其在表面下方相对于观察平面以小角度倾斜。高介电常数 PMN-PT 的次表面成像在通常用于铁电域结构成像的压电响应力显微镜中是困难的，并且证明 UAFM 对于分析次表面缺陷的 3D 结构很有用。总之，验证了SEP施加电场对于UAFM对铁电畴结构的无损评估是有用的。由此，建立了利用SEP对铁电体进行UAFM评价的基础，从而达到了最初的目的。