Nellist P D, Cosgriff E C, Behan G, Kirkland A I
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
Microsc Microanal. 2008 Feb;14(1):82-8. doi: 10.1017/S1431927608080057. Epub 2007 Dec 21.
Aberration correction leads to reduced focal depth of field in the electron microscope. This reduced depth of field can be exploited to probe specific depths within a sample, a process known as optical sectioning. An electron microscope fitted with aberration correctors for both the pre- and postspecimen optics can be used in a confocal mode that provides improved depth resolution and selectivity over optical sectioning in the scanning transmission electron microscope (STEM). In this article we survey the coherent and incoherent imaging modes that are likely to be used in scanning confocal electron microscopy (SCEM) and provide simple expressions to describe the images that result. Calculations compare the depth response of SCEM to optical sectioning in the STEM. The depth resolution in a crystalline matrix is also explored by performing a Bloch wave calculation for the SCEM geometry in which the pre- and postspecimen optics are defocused away from their confocal conditions.
像差校正会导致电子显微镜中的焦深减小。这种减小的焦深可用于探测样品内的特定深度，这一过程称为光学切片。配备有样品前和样品后光学系统像差校正器的电子显微镜可用于共聚焦模式，该模式在扫描透射电子显微镜（STEM）中提供比光学切片更高的深度分辨率和选择性。在本文中，我们概述了可能用于扫描共聚焦电子显微镜（SCEM）的相干和非相干成像模式，并给出了描述所得图像的简单表达式。通过计算比较了SCEM与STEM中光学切片的深度响应。还通过对样品前和样品后光学系统偏离共聚焦条件的SCEM几何结构进行布洛赫波计算，探索了晶体基质中的深度分辨率。
