Walker Christopher G H, Frank Luděk, Müllerová Ilona
Department of Electronics, University of York, Heslington, York, United Kingdom.
Institute of Scientific Instruments, Brno, Czech Republic.
Scanning. 2016 Nov;38(6):802-818. doi: 10.1002/sca.21330. Epub 2016 Jun 10.
The advent of new imaging technologies in Scanning Electron Microscopy (SEM) using low energy (0-2 keV) electrons has brought about new ways to study materials at the nanoscale. It also brings new challenges in terms of understanding electron transport at these energies. In addition, reduction in energy has brought new contrast mechanisms producing images that are sometimes difficult to interpret. This is increasing the push for simulation tools, in particular for low impact energies of electrons. The use of Monte Carlo calculations to simulate the transport of electrons in materials has been undertaken by many authors for several decades. However, inaccuracies associated with the Monte Carlo technique start to grow as the energy is reduced. This is not simply associated with inaccuracies in the knowledge of the scattering cross-sections, but is fundamental to the Monte Carlo technique itself. This is because effects due to the wave nature of the electron and the energy band structure of the target above the vacuum energy level become important and these are properties which are difficult to handle using the Monte Carlo method. In this review we briefly describe the new techniques of scanning low energy electron microscopy and then outline the problems and challenges of trying to understand and quantify the signals that are obtained. The effects of charging and spin polarised measurement are also briefly explored. SCANNING 38:802-818, 2016. © 2016 Wiley Periodicals, Inc.
利用低能量（0 - 2 keV）电子的扫描电子显微镜（SEM）中新成像技术的出现，带来了在纳米尺度研究材料的新方法。在理解这些能量下的电子传输方面，它也带来了新的挑战。此外，能量的降低带来了新的对比度机制，产生的图像有时难以解读。这使得对模拟工具的需求不断增加，特别是针对低电子撞击能量的模拟工具。几十年来，许多作者都采用蒙特卡罗计算来模拟电子在材料中的传输。然而，随着能量降低，与蒙特卡罗技术相关的误差开始增大。这不仅仅与散射截面知识的不准确有关，而且是蒙特卡罗技术本身的根本问题。这是因为电子的波动性质以及高于真空能级的靶材能带结构所产生的效应变得重要起来，而这些性质使用蒙特卡罗方法很难处理。在这篇综述中，我们简要描述了扫描低能量电子显微镜的新技术，然后概述了理解和量化所获得信号时存在的问题与挑战。还简要探讨了充电和自旋极化测量的影响。《扫描》38:802 - 818，2016年。© 2016威利期刊公司。
