EBSD geometry in the SEM: simulation and representation

Abstract

AbstractTo obtain a sufficient electron backscatter diffraction (EBSD) signal in the scanning electron microscope (SEM), the sample is highly tilted. This significantly increases both the backscatter yield and the percentage of electrons that are scattered in a forward direction, making them available for detection by the phosphor screen of the EBSD camera. Unlike a conventional Everhart–Thornley detector in SE mode, which collects electrons of multiple trajectories via an applied voltage, the exact position of the phosphor screen with respect to the sample determines what solid angle of the forward scattered electrons is detected. Poor positioning of the camera or an unfavorable working distance may result in patterns that are less than ideal, increasing the difficulty of automated indexing or phase identification. Accordingly, we have used a single‐scattering Monte Carlo model to simulate electron transport through tilted samples. Results of the simulations include tracking the spatial and energy distributions of the electrons during three phases of the process: within the interaction volume, on exiting the sample surface, and when reaching the phosphor screen. Subsequent analysis fosters a better understanding of the geometric requirements for EBSD. Furthermore, our graphical representation of the Monte Carlo results is, we feel, a significant improvement over ‘connect‐the‐dots’ figures typical of the literature, providing greater insight into the nature of the backscatter yield from tilted samples. Copyright © 2005 John Wiley & Sons, Ltd.