Do smaller probes in a scanning transmission electron microscope result in more precise measurement of the distances between atom columns?

摘要

Conventionally, the design of annular dark-field (ADF) scanning transmission electron microscopy (STEM) experiments is mostly based on resolution criteria related to direct visual interpretability. However, the future of image interpretation lies in quantitative structure determination. Since this is a different purpose, the design has to be reconsidered. In this paper, a precision-based performance measure is proposed, which follows from a simplified model. From this, the optimal experimental design for a quantitative ADF STEM experiment is derived. The outcome of this optimization is that the probe should not be as small as possible, but that the optimal width depends strongly on the material under investigation. Furthermore, it turns out that the radius of the hole in the detector should be as large as the optimal aperture radius. [References: 17]