The special properties of graphene can be largely influenced by point defects in the lattice. However, TEM studies of topological defects in few-layered graphene have rarely been reported. In this work, the two simplest forms of point defects monovacancy and divacancy in twisted bilayer graphene are characterized using aberration-corrected transmission electron microscopy (AC-TEM) at 80 kV. A convenient approach by using a negative mask in the fast Fourier transform (FFT) has been applied to separate the image signal of the two graphene layers. In the study combined with density functional theory (DFT) calculations and tight-binding molecular dynamics simulations, the analysis of the defect structure and movement shows the stability and migration behavior of both defects. DFT calculations indicate that the migration of monovacancy in bilayer graphene needs to overcome a higher energy barrier.

中文翻译：

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层状堆叠双层石墨烯中的点缺陷

石墨烯的特殊性能在很大程度上受晶格中点缺陷的影响。然而，很少报道几层石墨烯中的拓扑缺陷的TEM研究。在这项工作中，使用80 kV的像差校正透射电子显微镜（AC-TEM）对扭曲的双层石墨烯中点缺陷的两种最简单形式-单空位和双空位进行了表征。在快速傅里叶变换（FFT）中使用负掩模的便捷方法已应用于分离两个石墨烯层的图像信号。在研究中，结合密度泛函理论（DFT）计算和紧密结合的分子动力学模拟，对缺陷结构和运动的分析显示了两种缺陷的稳定性和迁移行为。