The Principle of TEM

A sample placed in an electron microscope

The transmission electron microscope (TEM) uses a beam of electrons to magnify and examine specimens. It is far more powerful than a light microscope, and its creators were awarded the Nobel Prize for its development.

Magnetic Lenses

Electromagnets are used to guide a narrow beam of electrons through a thin specimen and to a fluorescent screen, which creates an image. The magnets keep the beam concentrated to ensure high quality image resolution.

Scattering

As the electron beam passes through the specimen, some of the electrons interact with it and are scattered away from the beam. These gaps in the beam create a shadow on the fluorescent screen with varying degrees of darkness depending on the density of the specimen that they pass through.

Uses

While TEM requires a very thin sample, which can be difficult to produce, it is extremely powerful in resolving crystalline structures and the morphology of a specimen.

References

• Nobel Prize: The Transmission Electron Microscope
• Stanford: Transmission Electron Microscope (TEM) Facility