Energy Dispersive Spectroscopy (EDS)

Chemical Analysis

  • The chemical composition of a sample can be determined using x-ray analysis.
  • This is done by collecting and analysing the characteristic x-rays that are emitted by the sample during electron bombardment.
  • X-rays can be detected using either Energy Dispersive Spectroscopy (EDS) or Wavelength Dispersive Spectroscopy (WDS) techniques.

X-ray Generation

  • When an electron from a K-shell is replaced by one from the next closest shell (L), the energy released is designated as a x-ray.
  • When an electron from a K-shell is replaced by one from the second closest shell (M), the energy released is designated as a x-ray.
  • Each shell has a different energy level and as an electron drops shells the excess energy is released as a photon (γ) which is the x-ray.
  • These events cause a unique energy release and can be detected in the SEM using an energy-dispersive spectroscopy (EDS) detector.


Varying Accelerating Potential

  • Decreasing the accelerating potential of the electron beam will reduce the interaction volume
  • This decrease will increase the resolution of chemical analysis
  • However, some x-rays may not be detected by standard EDS detectors and specialist EDS detectors may be needed, like a windowless detector
  • Increasing the accelerating potential of the electron beam will increase the interaction volume
  • This increase will decrease the resolution, however, it will enable analysis of structures deeper into the sample, i.e. printed circuit board below a protective polymeric coating.