Domain walls are of increasing interest in ferroelectrics because of their unique properties and potential applications in future nanoelectronics. However, the thickness of ferroelastic domain walls remains elusive due to the challenges in experimental characterization. Here, we determine the atomic structure of ferroelastic domain walls and precisely measure the polarization and domain wall thickness at picometer scale using annular bright field imaging in an aberration-corrected scanning transmission electron microscope. We find that the domain wall thickness in PbZr0.2Ti0.8O3 and PbTiO3 thin films is typically about one-unit cell, across which the oxygen octahedron distortion behavior is in excellent agreement with first principles calculations. Remarkably, wider domain walls about two-unit cells in thickness are also observed for those domains walls are coupled with dislocations and underwent a compressive strain. These results suggest that the thickness of ferroelastic domain walls highly depends on their atomic environments. This study can help us to understand the past debatable experimental results and provide further insights into control of domain walls via strain engineering for their possible applications in nanoelectronics.

中文翻译：

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位错附近铁弹性畴壁的原子环境相关厚度

由于其独特的性质和在未来纳米电子学中的潜在应用，畴壁对铁电体越来越感兴趣。然而，由于实验表征方面的挑战，铁弹性畴壁的厚度仍然难以捉摸。在这里，我们确定了铁弹性畴壁的原子结构，并在像差校正的扫描透射电子显微镜中使用环形明场成像精确测量了皮米级的极化和畴壁厚度。我们发现 PbZr0.2Ti0.8O3 和 PbTiO3 薄膜的畴壁厚度通常约为一个晶胞，氧八面体畸变行为与第一性原理计算非常吻合。值得注意的是，还观察到厚度约为两个晶胞的更宽的畴壁，因为这些畴壁与位错耦合并经受压缩应变。这些结果表明铁弹性畴壁的厚度高度依赖于它们的原子环境。这项研究可以帮助我们了解过去有争议的实验结果，并为通过应变工程控制畴壁在纳米电子学中的可能应用提供进一步的见解。