- 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.
- When an electron from a K-shell is replaced by one from the next closest shell (L), the energy released is designated as a Kα 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 Kβ 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.
Mineral map of NWA 15189 where pink = Low-Ca pyroxene, orange = High-Ca pyroxene, dark green = Plagioclase and teal = silica
Low Voltage EDS
Relevant Case Studies
Are you interested in how PEMC have used this technique in research and industry? See examples of EDS applications on a range of projects below.
Classifying Meteorites with SEM
How PEMC is working with local meteorite dealers to give names to new meteorites
Low Energy Analysis with a Specialised Detector
Low energy analysis using Oxford Instruments' Ultim Extreme Detector
A Microscale Investigation of a 1000km Metamorphic Belt
Using electron microscope to reveal details about metamorphic processes
Electron Microscopy for Farmers
How PEMC have worked with multiple farmers for a deeper understanding of soil health and diversity though electron microscopy
Testing the Capabilities of Automated Mineralogy in Mining
Analysing mining samples using automated mineralogy software for resource recovery in the mining industry