利用压电力显微镜研究PMN-30%PT单晶体中铁电畴的结构及其演变

本文总结了我们近年米利用压电力显微镜(PFM)研究PMN-30%PT单晶体中铁电畴的结构及其演变的结果.选择PMN-30%PT品体是因为该组分在超声传感器等应用方面具有最大的潜力.铁电畴的观察是基于反压电现象;具体来讲就是当交变电场通过原子力显微镜探针加到晶体表面时,会引起品体表面的起伏振荡,而锁相放大器可以解出该振荡信号的振幅和相位角;其中振幅衬度反映了压电系数d33的大小,而相位衬度则反映了铁电畴的极化方向.文中介绍了平面内以及垂直平面的PFM成像技术,并演示了影响畴的图像的一些因素,其中包括静电倚效应,表层效应和机械抛光的影响.本文还利用有限无模型对PFM成像原理进行了模拟分析.着重研究了晶体中铁电畴的尺寸分布,畴与晶体取向,时间和温度的相关性,以及畴的演变过程.

STUDY OF FERROELECTRIC DOMAIN STRUCTURE AND EVOLUTION IN PMN-30% PT SINGLE CRYSTALS BY MEANS OF PIEZORESPONSE FORCE MICROSCOPY

In this paper we review our recent research in the study of domain configuration and evolu-tion in PMN-xPT single crystal by means of piezoresponse-force-microscopy (PFM). In particular, we focus on the PMN-30%PT single crystal since this PT content possesses the highest application potential in ultrasound transducers etc. The method to observe the ferroelectric domain structure is based on the reversed piezoelectric effect; while the electric field is applied through a conductive atomic force microscope (AFM) tip and the crystal surface oscillation is measured by AFM using a lock-in amplifier technique where the resolved amplitude reflects the magnitude of d33 and the phase contrast represents the ferroelec-tric domain orientation. The techniques of in-plane polarization and out-of-plane polarization PFM are in-troduced, and some effects to the domain imaging, such as static charge effect, skin effect and mechanical polishing effect, are illustrated. Domain-size distribution, crystal-orientation-dependent, time-dependent and temperature-dependent domain evolutions in the crystal are studied.