Hoque Shahedul, Ito Hiroyuki, Takaoka Akio, Nishi Ryuji
Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1 Mihogaoka, Ibaraki, Osaka 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. 2017 Nov;182:68-80. doi: 10.1016/j.ultramic.2017.06.014. Epub 2017 Jun 20.
We present N-SYLC (N-fold symmetric line currents) models to correct 5th order axial geometrical aberrations in electron microscopes. In our previous paper, we showed that 3rd order spherical aberration can be corrected by 3-SYLC doublet. After that, mainly the 5th order aberrations remain to limit the resolution. In this paper, we extend the doublet to quadruplet models also including octupole and dodecapole fields for correcting these higher order aberrations, without introducing any new unwanted ones. We prove the validity of our models by analytical calculations. Also by computer simulations, we show that for beam energy of 5keV and initial angle 10mrad at the corrector object plane, beam size of less than 0.5nm is achieved at the corrector image plane.
我们提出了N-SYLC（N重对称线电流）模型，以校正电子显微镜中的五阶轴向几何像差。在我们之前的论文中，我们表明三阶球差可以通过3-SYLC双合透镜校正。在此之后，主要是五阶像差仍然限制着分辨率。在本文中，我们将双合透镜扩展为四重透镜模型，该模型还包括八极场和十二极场，用于校正这些高阶像差，而不会引入任何新的有害像差。我们通过解析计算证明了我们模型的有效性。通过计算机模拟，我们还表明，对于校正器物平面处5keV的束能量和10mrad的初始角度，在校正器像平面处可实现小于0.5nm的束尺寸。
