Configuration and local elastic interaction of ferroelectric domains and misfit dislocation in PbTiO3/SrTiO3 epitaxial thin films
Configuration and local elastic interaction of ferroelectric domains and misfit dislocation in PbTiO3/SrTiO3 epitaxial thin films
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DOI：
10.1088/1468-6996/12/3/034413
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发表时间：
2011-06-01
影响因子：
5.5
通讯作者：
Konno, Toyohiko J.
中科院分区：
文献类型：
--
作者：
Kiguchi, Takanori;Aoyagi, Kenta;Konno, Toyohiko J.
我们利用几何相位分析（GPA）结合高分辨率透射电子显微镜（HRTEM）和高角度环形暗场扫描透射电子显微镜（HAADF-STEM），在纳米尺度上研究了PbTiO3/SrTiO3（001）外延薄膜中90度域周围的应变场和失配位错。这些薄膜通常包含 a/c 混合域和失配位错的组合。 PbTiO3 层由两种类型的 a 域（90 度域）组成：典型的 a/c 混合域配置，其中 a 域宽度为 20-30 nm，纳米级域宽度约为 3 nm。在后一种情况下，纳米尺寸的a域不接触薄膜/基底界面；它仍然远离界面并且源于失配位错。从 HRTEM 图像的 GPA 获得的应变图显示了 a 域和位错之间的弹性相互作用。它们之间的法向应变场和晶格旋转相互匹配。应变图显示 a 域成核发生在失配位错处。围绕失配位错的晶格旋转触发了 a 域的成核；失配位错周围的法向应变松弛了a域中的残余应变；然后，发生a域生长，伴随着垂直于失配位错的额外位错的引入，并且位错解离成具有APB的两对部分位错，APB是a域的底部边界。基于上述结果，提出了PbTiO3/SrTiO3外延体系中90度域成核和生长的新机制。
We have studied the strain field around the 90 degrees domains and misfit dislocations in PbTiO3/SrTiO3 ( 001) epitaxial thin films, at the nanoscale, using the geometric phase analysis (GPA) combined with high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). The films typically contain a combination of a/c-mixed domains and misfit dislocations. The PbTiO3 layer was composed from the two types of the a-domain (90 degrees domain): a typical a/c-mixed domain configuration where a-domains are 20-30 nm wide and nano sized domains with a width of about 3 nm. In the latter case, the nano sized a-domain does not contact the film/substrate interface; it remains far from the interface and stems from the misfit dislocation. Strain maps obtained from the GPA of HRTEM images show the elastic interaction between the a-domain and the dislocations. The normal strain field and lattice rotation match each other between them. Strain maps reveal that the a-domain nucleation takes place at the misfit dislocation. The lattice rotation around the misfit dislocation triggers the nucleation of the a-domain; the normal strains around the misfit dislocation relax the residual strain in a-domain; then, the a-domain growth takes place, accompanying the introduction of the additional dislocation perpendicular to the misfit dislocation and the dissociation of the dislocations into two pairs of partial dislocations with an APB, which is the bottom boundary of the a-domain. The novel mechanism of the nucleation and growth of 90 degrees domain in PbTiO3/SrTiO3 epitaxial system has been proposed based on above the results.