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首页> 外文学位 >The influence of crystal defects on domain wall motion in thin film Pb(Zr,Ti)O3.
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The influence of crystal defects on domain wall motion in thin film Pb(Zr,Ti)O3.

机译：晶体缺陷对薄膜Pb（Zr，Ti）O3中畴壁运动的影响。

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摘要

This work describes the interactions of domain walls in ferroelectric Pb(Zr,Ti)O3 with grain boundaries and PbO non-stoichiometry. This was studied for a variety of Zr:Ti ratios by analyzing the local piezoelectric response using band excitation piezoresponse force microscopy. Measurements were conducted on a variety of tilt and twist bicrystals with angles ranging from 10° to 30°. For the >15° tilt and ≥10° twist grain boundaries, a local minimum in the nonlinear response was observed at the grain boundary. The 10° tilt grain boundaries exhibited a maximum nonlinear response at the grain boundary.;Variations in the nonlinear response at a 24° tilt grain boundary was measured for three different Zr:Ti ratios. Films with a ratio of 20:80, far into the tetragonal regime, exhibited a complex distribution of nonlinear response alternating between low and high with distance from the grain boundary. Films with a ratio of 45:55 and 52:48, tetragonal and near morphotropic phase boundary rhombohedral, respectively, exhibited a minimum in nonlinear response at the grain boundary neighbored by a maximum in nonlinear response.;The nonlinear response was correlated to the domain structure. The domain structure was characterized before and after poling using piezoresponse force microscopy and transmission electron microscopy. It was found that the domain structure was controlled by the local strain and electric field for the largest angle grain boundaries. Domain walls were pinned at the grain boundary by the local strain and electric field. At 360-650 nm from the grain boundary, domain wall -- domain wall interactions dominated the nonlinear response. A smaller width of reduced nonlinear response for the film with Zr:Ti ratio of 52:48 was attributed to enhanced relaxation of the local strain and electric field due to the small ∼6 nm domain size.;Phase field models were used to determine the primary factors involved in forming domains at large angle tilt grain boundaries. The models suggest that domains form to minimize the local change in strain across the grain boundary, explaining correlated domain organization in neighboring grains previously observed by piezoresponse force microscopy and transmission electron microscopy. However, strain compatibility could not account for the observed formation of head to head domain structures observed at the grain boundary for Pb(Zr0.2Ti0.8)O3; it is believed that these are stabilized by built-in charge or additional stress compensation.;It was demonstrated that the pinning for 24° tilt angle grain boundaries influences domain wall motion over a longer lateral distance (0.45 -- 0.80 microm) than 30° twist angle grain boundaries (∼0.35 microm). Additionally, the pinning energy reduced with the grain boundary angle. The maximum in nonlinear response observed for small angle tilt grain boundaries (≤ 10°) was attributed to an increased concentration of low energy pinning sites reducing the reversible response and increasing the irreversible response. Similarly, minimal variation in the nonlinear response was observed at the grain boundary for intermediate grain boundary angles (15° tilt) due to the grain boundary energy being similar to other defects present in the film.;A furnace providing a controlled PbO atmosphere was developed so that the effect of PbO defects on the functional properties of Pb(Zr,Ti)O 3 could be determined. Minimal variation in the permittivity, Rayleigh parameters, and aging rates was observed for films with a range of PbO contents. A decreasing remanent polarization was observed with increasing PbO content in minor polarization -- electric field hysteresis loops. An increase in the area of low nonlinear response regions with decreasing PbO content was measured by band excitation piezoresponse force microscopy. This suggests that PbO deficiencies act to reduce domain wall motion where it is already low. It was determined that VPb″ -- VO″ defect dipoles, if they exist, have only a modest influence on domain wall motion compared to defects already present in the film.;This work helps to determine the mechanisms responsible for emergent properties in ferroelectric materials and, as such, provides a basis for superior models representing the functional properties of ferroelectric materials. The measurements of the effect of grain boundaries and PbO concentration on nonlinear response support the framework for the representations of mobile interfaces interacting with defects in materials. By correlating measurements by various characterization and modeling methods, a deeper understanding of ferroelectric materials is provided.
机译：这项工作描述了铁电性Pb（Zr，Ti）O3中的畴壁与晶界和PbO非化学计量的相互作用。通过使用带激励压电响应力显微镜分析局部压电响应，研究了各种Zr：Ti比率。对各种倾斜和扭曲双晶进行了测量，角度范围从10°到30°。对于> 15°倾斜和≥10°扭曲的晶界，在晶界处观察到非线性响应的局部最小值。 10°倾斜晶界在晶界处表现出最大的非线性响应。;对于三种不同的Zr：Ti比，测量了24°倾斜晶界处的非线性响应的变化。比例为20:80的薄膜，远处于四方晶系，表现出复杂的非线性响应分布，其低和高之间交替变化，且距晶界的距离较远。比例为45:55和52:48的薄膜，分别是四方晶相和近晶相相菱形，晶界处的非线性响应最小，非线性响应最大;非线性响应与畴相关结构体。在极化前后使用压电响应力显微镜和透射电子显微镜对畴结构进行了表征。发现在最大角度晶界处，区域结构受局部应变和电场控制。通过局部应变和电场将畴壁钉在晶粒边界上。在距晶界360-650 nm处，畴壁-畴壁相互作用主导了非线性响应。 Zr：Ti比为52:48的薄膜具有较小的减小的非线性响应宽度，这归因于较小的〜6 nm畴尺寸，从而增强了局部应变和电场的弛豫。在大角度倾斜晶粒边界形成畴所涉及的主要因素。这些模型表明，畴的形成是为了使整个晶界的应变的局部变化最小，从而解释了先前通过压电响应力显微镜和透射电子显微镜观察到的相邻晶粒中的相关畴组织。但是，应变相容性不能解释在Pb（Zr0.2Ti0.8）O3的晶界观察到的头对头畴结构的形成。可以相信，通过内置电荷或额外的应力补偿可以稳定这些壁垒;已证明，倾斜角为24°的晶界钉扎会在比30°长的横向距离（0.45-0.80微米）上影响畴壁运动扭曲角晶界（约0.35微米）。另外，钉扎能量随晶界角减小。小角度倾斜晶界（≤10°）观察到的最大非线性响应归因于低能钉扎位点的浓度增加，从而降低了可逆响应并增加了不可逆响应。类似地，由于晶界能量与薄膜中存在的其他缺陷相似，在中间晶界角（倾斜15°）下，在晶界处观察到非线性响应的最小变化。;开发了一种可控PbO气氛的熔炉因此可以确定PbO缺陷对Pb（Zr，Ti）O 3的功能性能的影响。对于具有一系列PbO含量的薄膜，介电常数，瑞利参数和老化速率的变化最小。随着较小的极化-电场磁滞回线中PbO含量的增加，剩余极化强度降低。通过带激发压电响应力显微镜测量了随着PbO含量的降低，低非线性响应区域的面积增加。这表明PbO缺陷会降低已经很低的畴壁运动。可以确定，与膜中已经存在的缺陷相比，VPb“-VO”缺陷偶极子（如果存在）对畴壁运动仅具有中等影响。;这项工作有助于确定造成铁电材料中新兴特性的机理。因此，它为代表铁电材料功能特性的高级模型提供了基础。晶界和PbO浓度对非线性响应的影响的测量结果支持了与材料中的缺陷相互作用的移动界面的表示框架。通过各种表征和建模方法对测量值进行关联，可以提供对铁电材料的更深入了解。

著录项

  • 作者

    Marincel, Daniel M.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Materials science.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 170 p.
  • 总页数 170
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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