The influence of beam energy and oxidation on quantitative carbide analysis in the scanning electron microscope

Abstract

In this paper the origin of the carbide/matrix contrast in secondary electron images and its ramifications for spatial resolution are investigated. A profound influence of the backscattered electron yield and the oxidation of the steel matrix was found, which manifests itself in a contrast reversal at low primary electron beam energies. The authors established that low beam energies are necessary to obtain the required spatial resolution. Strategies for optimizing the contrast between carbide and matrix in secondary electron images without compromising the spatial resolution are presented. A simple method to estimate the thickness of thin oxide layers from low voltage secondary electron images is also described.