Convergent beam electron diffraction is routinely applied for studying deformation and local strain in thick crystals by matching the crystal structure to the observed intensity distributions. Recently, it has been demonstrated that CBED can be applied for imaging two-dimensional (2D) crystals where a direct reconstruction is possible and three-dimensional crystal deformations at a nanometre resolution can be retrieved. Here, we demonstrate that second-order effects allow for further information to be obtained regarding stacking arrangements between the crystals. Such effects are especially pronounced in samples consisting of multiple layers of 2D crystals. We show, using simulations and experiments, that twisted multilayer samples exhibit extra modulations of interference fringes in CBED patterns, i. e., a CBED moiré. A simple and robust method for the evaluation of the composition and the number of layers from a single-shot CBED pattern is demonstrated.

中文翻译：

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多层范德华结构的会聚束电子衍射

通过将晶体结构与观察到的强度分布相匹配，会聚束电子衍射通常用于研究厚晶体的变形和局部应变。最近，已经证明 CBED 可用于二维 (2D) 晶体的成像，其中可以直接重建，并且可以检索纳米分辨率的三维晶体变形。在这里，我们证明了二阶效应允许获得关于晶体之间堆叠排列的更多信息。这种效果在由多层 2D 晶体组成的样品中尤为明显。我们使用模拟和实验表明，扭曲的多层样品在 CBED 图案中表现出额外的干涉条纹调制，即 CBED 莫尔条纹。