An unusually broad bell-shaped component (BSC) has been previously observed in surface electron diffraction on different types of 2D systems. It was suggested to be an indicator of uniformity of epitaxial graphene (Gr) and hexagonal boron nitride (hBN). In the current study we use low-energy electron microscopy and micro-diffraction to directly relate the BSC to the crystal quality of the diffracting 2D material. Specially designed lateral heterostructures were used to map the spatial evolution of the diffraction profile across different 2D materials, namely pure hBN, BCN alloy and pure Gr, where the alloy region exhibits deteriorated structural coherency. The presented results show that the BSC intensity has a minimum in the alloyed region, consequently showing that BSC is sensitive to the lateral domain size and homogeneity of the material under examination. This is further confirmed by the presence of a larger number of sharp moir spots when the BSC is most pronounced in the pure hBN and Gr regions. Consequently, it is proposed that the BSC can be used as a diagnostic tool for determining the quality of the 2D materials.

以前在不同类型的二维系统的表面电子衍射中观察到了一个异常宽的钟形分量 (BSC)。它被认为是外延石墨烯（Gr）和六方氮化硼（hBN）均匀性的指标。在目前的研究中，我们使用低能电子显微镜和微衍射将 BSC 与衍射二维材料的晶体质量直接联系起来。特殊设计的横向异质结构用于绘制不同二维材料（即纯 hBN、BCN 合金和纯 Gr）衍射分布的空间演变，其中合金区域表现出劣化的结构相干性。所呈现的结果表明，BSC 强度在合金化区域具有最小值，因此表明 BSC 对被检查材料的横向域大小和均匀性敏感。当 BSC 在纯 hBN 和 Gr 区域中最明显时，存在大量尖锐的莫尔斑点进一步证实了这一点。因此，建议将 BSC 用作确定 2D 材料质量的诊断工具。