First-principles simulation of light-ion microscopy of graphene
First-principles simulation of light-ion microscopy of graphene
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DOI：
10.1088/2053-1583/ac8e7e
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发表时间：
2022-01
期刊：
影响因子：
5.5
通讯作者：
A. Kononov;Alexandra Olmstead;A. Baczewski;A. Schleife
中科院分区：
文献类型：
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作者：
A. Kononov;Alexandra Olmstead;A. Baczewski;A. Schleife
2D材料对缺陷和纳米结构的极端敏感性需要精确的成像技术来验证原子几何结构中存在期望的特征和不存在不期望的特征。氦离子束已成为一种有前途的材料成像工具，其分辨率和景深比传统或环境扫描电子显微镜高20倍。在这里，我们提供了第一原理的理论见解，以推进离子束成像的原子级薄材料，通过执行实时时间依赖密度泛函理论模拟的单次冲击的10-200 keV的光离子在独立的石墨烯。我们预测，检测从材料背面（离子退出的一侧）发射的电子将导致高达三倍的信号和高达五倍的对比度图像，使2D材料成为离子束显微镜特别引人注目的目标。这种预测的出射侧发射的优越性可能来自各向异性的动力学发射。在石墨烯中诱导的电荷在亚fs时间尺度上平衡，导致碳晶格中仅轻微的扰动，对于本文研究的任何光束参数，这些扰动不太可能损坏原子结构。
The extreme sensitivity of 2D materials to defects and nanostructure requires precise imaging techniques to verify presence of desirable and absence of undesirable features in the atomic geometry. Helium-ion beams have emerged as a promising materials imaging tool, achieving up to 20 times higher resolution and 10 times larger depth-of-field than conventional or environmental scanning electron microscopes. Here, we offer first-principles theoretical insights to advance ion-beam imaging of atomically thin materials by performing real-time time-dependent density functional theory simulations of single impacts of 10–200 keV light ions in free-standing graphene. We predict that detecting electrons emitted from the back of the material (the side from which the ion exits) would result in up to three times higher signal and up to five times higher contrast images, making 2D materials especially compelling targets for ion-beam microscopy. This predicted superiority of exit-side emission likely arises from anisotropic kinetic emission. The charge induced in the graphene equilibrates on a sub-fs time scale, leading to only slight disturbances in the carbon lattice that are unlikely to damage the atomic structure for any of the beam parameters investigated here.