In transmission electron microscope (TEM), both the amplitude and the phase of electron beam change when electrons traverse a specimen. The amplitude is easily obtained by the square root of the intensity of a TEM image, while the phase affects defocused images. In order to obtain the phase map and verify the theoretical model of the interaction between electron beam and specimen, a lot of simulations have to be performed by researchers. In this work, we have simulated defocus images of a SiC nanowire in TEM with the method of electron optics. Mean inner potential and charge distribution on the nanowire have been considered in the simulation. Besides, due to electron scattering, coherence loss of the electron beam has been introduced. A dynamic process with Bayesian optimization was used in the simulation. With the infocus image as input and by adjusting fitting parameters, the defocus image is determined with a reasonable charge distribution. The calculated defocus images are in a good agreement with the experimental ones. Here, we present a complete solution and verification method for solving nanoscale charge distribution in TEM.

中文翻译：

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具有大离焦距离的 TEM 中带电纳米线的成像模拟

在透射电子显微镜 (TEM) 中，当电子穿过样品时，电子束的幅度和相位都会发生变化。振幅很容易通过 TEM 图像强度的平方根获得，而相位影响散焦图像。为了获得相图并验证电子束与试样相互作用的理论模型，研究人员必须进行大量的模拟。在这项工作中，我们使用电子光学方法在 TEM 中模拟了 SiC 纳米线的散焦图像。在模拟中已经考虑了纳米线上的平均内部电位和电荷分布。此外，由于电子散射，引入了电子束的相干损失。在模拟中使用了具有贝叶斯优化的动态过程。以离焦图像为输入，通过调整拟合参数，确定具有合理电荷分布的散焦图像。计算得到的散焦图像与实验图像吻合良好。在这里，我们提出了解决 TEM 中纳米级电荷分布的完整解决方案和验证方法。