Image Contrast in Energy-Filtered BSE Images at Ultra-Low Accelerating Voltages

Abstract

Scanning electron microscopy (SEM) at ultra-low landing energies reveals information at the topmost layer of the specimen surface, but the backscattered electron image contrast for certain specimens can be unusual. For primary electron energies above 1 keV, backscattered electron (BSE) yields from a specimen increase with increasing atomic number, providing a brighter image for heavier elements. However, at an electron beam energy of 0.2 keV, a reversal occurs; the BSE yield is greater for light elements than for heavier elements. The effect has been demonstrated for specimens of Au and Si in an SEM with an energyfiltering BSE detector.