Scanning electron microscopes scans the beam of
electrons over said specimen to produce a magnified
image of an object. There is another form of electron
microscope that is a little more similar to a SEM,
which is a TEM or transmission electron
microscope. I’m covering the SEM to save time, but
TEM are more powerful then SEMs and take more
time to prepare the specimen. The following is the
basic layout and function of a SEM.
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 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.