Scanning Electron Microscopy (SEM)

Definition - What does Scanning Electron Microscopy (SEM) mean?

Scanning electron microscopy (SEM) is a kind of electron microscope that produces images of a specimen by scanning it with a focused beam of electrons.

SEM delivers high-resolution surface data and greater materials contrast. They are widely used in electron microscopy sciences and application fields:

  • Nanotechnology
  • Materials analysis
  • Semiconductor failure analysis
  • Life sciences
  • Quality assurance

Environmental SEM (ESEM) is especially useful for non-metallic and biological materials because coating with carbon or gold is unnecessary. ESEM makes it possible to accomplish X-ray microanalysis on uncoated non-conductive samples.

Corrosionpedia explains Scanning Electron Microscopy (SEM)

Scanning electron microscopy uses a focused beam of high-energy electrons to produce a diversity of signals at the surface of solid specimens. The signals that derive from electron-sample interactions disclose information about the sample, including:

  • External morphology (texture)
  • Chemical composition
  • Crystalline structure
  • Orientation of materials

The electron beam is usually scanned in a raster scan pattern, and the beam's position is joined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Samples can be perceived in high vacuum, in low vacuum, and (in environmental SEM) in wet conditions.

SEM's advantages over traditional microscopes include:

  • Large depth of field - This allows more of a specimen to be in focus at one time.
  • Much higher resolution - Specimens can be magnified at much higher levels.
  • Microanalysis - Advanced microscopes can tell researchers information about its composition.

All of these advantages make the scanning electron microscope one of the most useful instruments in modern research.

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