Working Principle – EDS system

As a result of the interaction between high energy electrons and a sample under investigation in an electron microscope, the atoms of this sample are caused to emit X-rays.

An EDS system makes use of the fact that atoms of different chemical elements emit X-rays of different, characteristic energy. The evaluation of the energy spectrum collected by an energy dispersive Si(Li) or silicon drift X-ray detector (SDD) allows the determination of the qualitative and quantitative chemical sample composition at the current beam position.

This technique provides a very high spatial resolution since the information is obtained from a very small sample volume in the order of only a few microns. It is therefore also referred to as X-ray microanalysis. Up to date scanning electron microscopes (SEM) can operate with low beam energies and even further increase spatial resolution to the nanometer range. This resolution is also attained by (scanning) transmission electron microscopes (S/TEM).

When used with scanning microscopes, both SEM and STEM, the EDS system can analyze element distributions along a line (line scan) or within an area of interest (mapping).

Another advantage of the energy dispersive X-ray spectroscopy is that all elements from atomic number 4 (beryllium) up to 95 (americium) contained in the sample can be detected and analyzed simultaneously.