Strain analysis by nano-beam electron diffraction allows for measurements of strain with nanometre resolution in a large field of view. This is done by evaluating distances between diffraction discs in diffraction patterns acquired while a focussed electron beam is scanned across the sample in a transmission electron microscope. The bottleneck of this method is a precise determination of diffraction disc positions, which suffers from the inner structure of the discs caused by dynamical diffraction. Electron beam precession is a tool that solves this problem but it is not commonly available in every microscope. Without precession significant progress has been reported recently by using patterned condenser apertures. The pattern of the aperture is reproduced in patterns of the diffraction discs allowing for a more precise position determination. In this report the accuracy of measured strain profiles using patterned apertures is investigated by evaluation of realistic simulations. This is done especially at interfaces between regions with different lattice plane spacing. It is found by evaluation of the simulations that measured strain profiles are more blurred and hence the accuracy at the interface is worse the more patterns are imprinted to the condenser aperture. An explanation of this effect is given and as a proof of principle a solution to this problem is provided applying geometric phase analysis ptychography.

中文翻译：

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在 4D-STEM 中准确测量界面应变：各种方法的比较

通过纳米束电子衍射进行的应变分析允许在大视场中以纳米分辨率测量应变。这是通过评估衍射图案中衍射盘之间的距离来完成的，同时聚焦电子束在透射电子显微镜中扫描样品。这种方法的瓶颈是衍射盘位置的精确确定，它受到动态衍射引起的盘内部结构的影响。电子束进动是解决此问题的工具，但并非在每个显微镜中都普遍可用。最近通过使用图案化的聚光器孔径报告了在没有进动的情况下取得的重大进展。孔径的图案以衍射盘的图案再现，允许更精确的位置确定。在本报告中，通过对真实模拟的评估，研究了使用图案孔测量应变分布的准确性。这尤其在具有不同晶格平面间距的区域之间的界面处进行。通过对模拟的评估发现，测量的应变分布更模糊，因此界面处的精度越差，印记到聚光镜孔径的图案越多。给出了这种效应的解释，作为原理证明，提供了应用几何相位分析 ptychography 的解决方案。通过对模拟的评估发现，测量的应变分布更模糊，因此界面处的精度越差，印记到聚光镜孔径的图案越多。给出了这种效应的解释，作为原理证明，提供了应用几何相位分析 ptychography 的解决方案。通过对模拟的评估发现，测量的应变分布更模糊，因此界面处的精度越差，印记到聚光镜孔径的图案越多。给出了这种效应的解释，作为原理证明，提供了应用几何相位分析 ptychography 的解决方案。