Beam voltage effects in the study of embedded biological materials by secondary electron detectors

Thin and semithin sections were extensively examined by the secondary electron (SE) detector in a conventional scanning electron microscope (SEM), and in a transmission electron microscope with a scanning attachment (STEM). Various parameters, in particular the beam voltage, were shown to affect the final SE image (SEI). As for SEM observation, a surface contrast was imaged at low primary electron (PE) voltages (0.6-2 kV), whereas a subsurface contrast predominated at higher energies (15-30 kV). In STEM, significant differences were not detected by varying the PE in the 20-100 kV range. Surface and subsurface information was simultaneously imaged even though the SEI were better resolved at the highest energy.