How a scanning electron microscope (SEM) works?

scanning electron microscope scans a beam of electrons over a specimen to produce a magnified image of an object. That’s completely different from a TEM, where the beam of electrons goes right through the specimen.

  1. Electrons are fired into the machine.
  2. The main part of the machine (where the object is scanned) is contained within a sealed vacuum chamber because precise electron beams can’t travel effectively through the air.
  3. A positively charged electrode (anode) attracts the electrons and accelerates them into an energetic beam.
  4. An electromagnetic coil brings the electron beam to a very precise focus, much like a lens.
  5. Another coil, lower down, steers the electron beam from side to side.
  6. The beam systematically scans across the object being viewed.
  7. Electrons from the beam hit the surface of the object and bounce off it.
  8. A detector registers these scattered electrons and turns them into a picture.
  9. A hugely magnified image of the object is displayed on a TV screen.