铁电畴的扫描力显微镜检测方法研究

【作者】 李松霞；

【导师】 包生祥；

【作者基本信息】 电子科技大学 ， 材料学， 2003， 硕士

【摘要】 铁电畴的结构及其运动规律直接决定了铁电体的物理性质及其应用方向，电畴的检测是进行铁电特性研究的前提条件。现有的铁电畴检测手段，如偏光显微镜、粉末花样技术、扫描电镜、透射电镜、扫描电子声显微镜等存在这样或那样的缺点：诸如制样繁琐、易破坏原始畴结构、或畴结构成像分辨率还不够高等。扫描力显微镜(SFM)是源于原子力显微镜的一类与力作用技术相关的显微仪器总称。由于其操作简便、样品无需特别制备、能高灵敏度地探测探针-样品表面之间各种作用力，具有极高的成像分辨率，故自它诞生之日起即被各学科领域所关注。为了获得高分辨、简易和非破坏的铁电畴检测方法，SFM不失为一种有效的研究手段。本文利用电压调制SFM研究铁电畴的检测方法。探讨SFM检测电畴的不同机理和成像模式，从理论上分析了压电响应原子力显微镜（PFM）、扫描非线性介电显微镜（SNDM）和开尔文力显微镜（KFM）检测电畴的成像原理；实验研究了电压、作用力、探针等的改变对电畴成像的影响。针对给定的样品进行了仪器参数优化：当交流电压振幅Vac≥3V（小于反转电压），频率f=5~20kHz时使用导电微悬臂DF3-R能够得到PMN-PT铁电单晶的清晰电畴结构图像。在研究PFM检测电畴的过程中，为了减弱甚至消除静电力的干扰，对不同微悬臂、施加电压等因素逐一进行分析研究。结果表明，采用弹性系数较大的探针能够有效的减小静电力的干扰。采用改装的直流电源成功地对样品进行了反转，并利用PFM研究了铁电畴的极化反转。本工作的结果为今后研究铁电薄膜材料的电畴结构打下了基础，也为研究铁电块材的疲劳、极化弛豫等特性提供了有效手段更多还原

【Abstract】 Domain structure and its movement determine the physical properties of ferroelectrics. Investigation of domains is the precondition to study macroscopic properties of ferroelectrics. There are many methods to investigate domains, such as polarization microscopy, scanning electron microscopy, transmission electron microscopy, scanning electron acoustic microscopy and so on. However, these methods suffer from some serious disadvantages involving complex sample preparation, damage to sample, low resolution. Scanning Force Microscopy (SFM), which roots from atomic force microscopy, is a general designation of microscopy relating to force behavoir technology. Because of its simple operation, high resolution without the need for special sample preparation, SFM is paid great attention in all scientific fields. SFM is an effective method to study domains with high resolution and nondestructive measuring. This paper studies the investigation methods of domain using voltage-modulated SFM. Different principles and modes of SFM are discussed. The imaging principle of piezoresponse atomic force microscopy, scanning nonlinear dielectric microscopy, Kelvin force microscopy are theoretically analysed, and the influence of voltage, contact force and microcantilever on the domain investigation is studied. The parameters of instrument are optimized using the same sample. And the result is that the domain structure of PMN-PT can be achieved successfully using DF3-R microcantilever when Vac≥3V, f=5-20kHz. Different cantilevers and electric fields are studied respectively in order to weaken and even eliminate the effect of electrostatic force. The results show that the influence of electrostatic can be diminished effectively when using cantilever with high spring coefficient.The work provides not only the foundation of studying domain structure in ferroelectric thin films but also the means of studying fatigue and polarization retention in ferroelctrics更多还原