Please enable JavaScript.

Coggle requires JavaScript to display documents.

The electron microscope - Coggle Diagram

- - - - Difficulties preparing the specimen limit the resolution that can be achieved
      - A higher energy electron beam is required and this may destroy the specimen.
    - - The whole system must be in a vacuum and therefore living specimens cannot be observed
      - A complex 'staining' process is required and even then the image is not in colour
      - The specimen must be extremely thin
      - The image may contain artefacts. Artefacts are things that result from the way the specimen is prepared. Artefacts may appear on the finished photomicrograph but are not part of the natural specimen. It is therefore not always easy to be sure that what we see on a photomicrograph really exists in that room.
  - - - Basically similar to a TEM, the SEM directs a beam of electrons on to the surface of the specimen from above, rather than penetrating it from below. The beam is the passed back and forth across a portion of the specimen in a regular pattern. The electrons are scattered by the specimen and the pattern of this scattering depends on the contours of the specimen surface.
        
        We can build up a 3D image by computer analysis of the pattern of scattered electrons and secondary electrons produced. The basic SEM has a lower resolving power than a TEM, around 20nm, but is still 10 times better than a light microscope.