Image-Histogram-based Secondary Electron Counting to Evaluate Detective Quantum Efficiency in SEM

TL;DR

This paper introduces a histogram-based method for accurately measuring the Detective Quantum Efficiency in SEM by directly counting secondary electrons, avoiding Poisson assumptions and enabling better performance evaluation.

Contribution

The paper presents a novel histogram-based technique for measuring DQE in SEM that does not rely on Poisson distribution assumptions, improving accuracy across various conditions.

Findings

DQE varies with working distance in SEM.

Histogram-based counting provides more accurate DQE measurements.

Method applicable to diverse imaging scenarios.

Abstract

Scanning electron microscopy is a powerful tool for nanoscale imaging of organic and inorganic materials. An important metric for characterizing the limits of performance of these microscopes is the Detective Quantum Efficiency (DQE), which measures the fraction of emitted secondary electrons (SEs) that are detected by the SE detector. However, common techniques for measuring DQE approximate the SE emission process to be Poisson distributed, which can lead to incorrect DQE values. In this paper, we introduce a technique for measuring DQE in which we directly count the mean number of secondary electrons detected from a sample using image histograms. This technique does not assume Poisson distribution of SEs and makes it possible to accurately measure DQE for a wider range of imaging conditions. As a demonstration of our technique, we map the variation of DQE as a function of working distance in the microscope.