Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1 Mihogaoka, Ibaraki, Ibaraki 567-0047, Japan; Hitachi High-Technologies Corporation, 882, Ichige, Hitachinaka, Ibaraki 312-8504, Japan.
Hitachi High-Technologies Corporation, 882, Ichige, Hitachinaka, Ibaraki 312-8504, Japan.
Ultramicroscopy. 2018 Apr;187:135-143. doi: 10.1016/j.ultramic.2018.02.002. Epub 2018 Feb 16.
In our previous works, we have proposed N-SYLC (N-fold symmetric line currents) models for aberration correction. In this paper, we propose "in-lens N-SYLC" model, where N-SYLC overlaps rotationally symmetric lens. Such overlap is possible because N-SYLC is free of magnetic materials. We analytically prove that, if certain parameters of the model are optimized, an in-lens 3-SYLC (N = 3) doublet can correct 3rd order spherical aberration. By computer simulation, we show that the required excitation current for correction is less than 0.25 AT for beam energy 5 keV, and the beam size after correction is smaller than 1 nm at the corrector image plane for initial slope less than 4 mrad.
在我们之前的工作中，我们提出了用于像差校正的 N-SYLC（N 重对称线电流）模型。在本文中，我们提出了“透镜内 N-SYLC”模型，其中 N-SYLC 与旋转对称透镜重叠。这种重叠是可能的，因为 N-SYLC 不含磁性材料。我们从理论上证明，如果优化模型的某些参数，则透镜内的 3-SYLC（N=3）双联体可以校正三阶球差。通过计算机模拟，我们表明对于束能 5keV，校正所需的激励电流小于 0.25AT，并且对于初始斜率小于 4mrad，在校正器图像平面上校正后的束径小于 1nm。
