Contrast effects using a two-detector system in low-voltage scanning electron microscopy

A system of two opposite Everhart-Thornley detectors A and B has formerly been applied in conventional SEM for electron energies between 5 and 20 keV to separate material, topographic and other types of contrast by sum and difference signals. This technique can also be used successfully for low-voltage scanning electron microscopy. The decreasing information depth with decreasing electron energy shows differences in the surface composition and contamination which cannot be observed beyond 5 keV. Also below 5 keV material and topographic contrast can be separated and increased by the A + B and A - B signals, respectively.