Environmental scanning electron microscope

A scanning electron microscope permitting a controlled gaseous specimen environment while maintaining the electron column at lower pressure by differential pumping. Ionization of the gas supplies positive ions that can neutralize negative specimen charging, and a suitable gaseous detector collects electron signals. This enables examination of some nonconducting uncoated specimens, with gas scattering and detector response included in interpretation.

A secondary-electron detector using amplification through collisions in the specimen-chamber gas. Its field drives signal electrons toward collection while positive ions can move toward a negatively charging specimen. Operating pressure and electrode geometry control amplification and background.