The interaction of oxygen vacancies and ferroelectric domain walls is of great scientific interest because it leads to different domain-structure behaviors. Here, we use high-resolution scanning transmission electron microscopy to study the ferroelectric domain structure and oxygen-vacancy ordering in a compressively strained Bi_0.9Ca_0.1FeO_3−δ thin film. It was found that atomic plates, in which agglomerated oxygen vacancies are ordered, appear without any periodicity between the plates in out-of-plane and in-plane orientation. The oxygen non-stoichiometry with δ ≈ 1 in FeO_2−δ planes is identical in both orientations and shows no preference. Within the plates, the oxygen vacancies form 1D channels in a pseudocubic [010] direction with a high number of vacancies that alternate with oxygen columns with few vacancies. These plates of oxygen vacancies always coincide with charged domain walls in a tail-to-tail configuration. Defects such as ordered oxygen vacancies are thereby known to lead to a pinning effect of the ferroelectric domain walls (causing application-critical aspects, such as fatigue mechanisms and countering of retention failure) and to have a critical influence on the domain-wall conductivity. Thus, intentional oxygen vacancy defect engineering could be useful for the design of multiferroic devices with advanced functionality.

中文翻译：

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带负电荷的面内和面外畴壁与钙掺杂铋-铁氧体薄膜中的氧空位团聚

氧空位和铁电畴壁的相互作用具有重要的科学意义，因为它会导致不同的畴结构行为。在这里，我们使用高分辨率扫描透射电子显微镜来研究压缩应变 Bi _0.9 Ca _0.1 FeO _3-δ薄膜中的铁电畴结构和氧空位排序。发现其中聚集的氧空位有序的原子板在面外和面内取向的板之间没有任何周期性出现。FeO _{2−δ 中}δ ≈ 1 的氧非化学计量平面在两个方向上都是相同的，并且没有任何偏好。在板内，氧空位在伪立方 [010] 方向上形成一维通道，具有大量空位，与具有少量空位的氧柱交替。这些氧空位板总是与带电畴壁以尾对尾配置重合。因此，已知诸如有序氧空位之类的缺陷会导致铁电畴壁的钉扎效应（导致应用关键方面，例如疲劳机制和抵抗保持失效）并对畴壁电导率产生关键影响。因此，有意的氧空位缺陷工程可用于设计具有先进功能的多铁性器件。