Scanning Electron Microscopy


To correlate an electron image with surface properties requires thorough understanding of electron-solid interaction, secondary electron emission mechanism and operation functions of image detectors. We emphasize the importance and usefulness of combining electron spectroscopy with scanning electron microscope in interpreting electron image contrast. Linear relationships among secondary electron image (SEI) brightness, total emission current and the integration of electron energy distribution were measured. We propose that channeling effect, instead of primary electron diffraction, is the crystallographic cause of SEI contrast. Secondary electrons contribute most to SEI brightness because of their high constituent in total yield, not because of high efficiency of SEI detector in detecting slow electrons. We show that work function change alone cannot explain the SEI brightness change during gas exposure. Rather, the brightness change is associated with changes of the entire spectrum. The possibility of measuring spectral response of energy analyzers is discussed in conjunction with the comparison of spectra taken with different analyzers.

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