Selective Backscattered Electron Imaging of Material and Channeling Contrasts in Microstructures of Scale on Low Carbon Steel Controlled by Accelerating Voltage and Take-off Angle

Abstract

The behaviors of contrasts in backscattered electron (BSE) images of cross-sectional heat-treated steel are studied under various accelerating voltages and take-off angle conditions. Changes in these conditions resulted in dramatic changes in contrasts. Low accelerating voltages and low take-off angles improve surface information and channeling contrasts, whereas high accelerating voltages and high take-off angles enhance bulk information and reduce channeling contrasts, resulting in improved Z contrast. These behaviors can be understood by the ratio of LLE (Low-Loss Electron), which are related to channeling contrasts, to the inelastic BSE components detected. The distribution of these components varies depending on the accelerating voltage and take-off angle, in that the detection ratio of LLE to inelastic BSE increases with decreasing accelerating voltages and take-off angles. The results obtained in this study can be used for obtaining Z and crystallographic information separately in BSE images for the material of interest.