Scanning precession electron diffraction (SPED) enables the local crystallography of materials to be probed on the nanoscale by recording a two-dimensional PED pattern at every probe position as a dynamically rocking electron beam is scanned across the specimen. SPED data from nanocrystalline materials commonly contain some PED patterns in which diffraction is measured from multiple crystals. To analyse such data, it is important to perform nanocrystal segmentation to isolate both the location of each crystal and a corresponding representative diffraction signal. This also reduces data dimensionality significantly. Here, two approaches to nanocrystal segmentation are presented, the first based on virtual dark-field imaging and the second on non-negative matrix factorisation. Relative merits and limitations are compared in application to SPED data obtained from partly overlapping nanoparticles, and particular challenges are highlighted associated with crystals exciting the same diffraction conditions. It is demonstrated that both strategies can be used for nanocrystal segmentation without prior knowledge of the crystal structures present, but also that segmentation artefacts can arise and must be considered carefully. The analysis workflows associated with this work are provided open-source. This article is protected by copyright. All rights reserved.

中文翻译：

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扫描进动电子衍射数据中的纳米晶体分割

扫描进动电子衍射 (SPED) 通过在每个探针位置记录二维 PED 图案，当动态摇摆的电子束扫描样品时，可以在纳米尺度上探测材料的局部晶体学。来自纳米晶体材料的 SPED 数据通常包含一些 PED 图案，其中从多个晶体测量衍射。为了分析这些数据，重要的是执行纳米晶体分割以隔离每个晶体的位置和相应的代表性衍射信号。这也显着降低了数据维度。在这里，介绍了两种纳米晶体分割方法，第一种基于虚拟暗场成像，第二种基于非负矩阵分解。比较了从部分重叠的纳米粒子获得的 SPED 数据的应用中的相对优点和局限性，并强调了与激发相同衍射条件的晶体相关的特殊挑战。结果表明，这两种策略都可以用于纳米晶体分割，而无需事先了解存在的晶体结构，但也可能出现分割伪影，必须仔细考虑。与这项工作相关的分析工作流程是开源的。本文受版权保护。版权所有。结果表明，这两种策略都可以用于纳米晶体分割，而无需事先了解存在的晶体结构，但也可能出现分割伪影，必须仔细考虑。与这项工作相关的分析工作流程是开源的。本文受版权保护。版权所有。结果表明，这两种策略都可以用于纳米晶体分割，而无需事先了解存在的晶体结构，但也可能出现分割伪影，必须仔细考虑。与这项工作相关的分析工作流程是开源的。本文受版权保护。版权所有。