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Overview of energy-dispersive X-ray spectroscopy technology
Elemental analysis is the fundamental application of energy-dispersive X-ray spectroscopy (EDS, EDX, or XEDS). EDS adds vital compositional information to electron microscopy images, enabling a comprehensive morphological and chemical overview of your sample.
Modern Scanning Transmission Electron Microscopy (S/TEM) X-ray analysis employs energy-dispersive X-ray spectroscopy (EDX) technology. In this process, the electron beam ejects atomic core-shell electrons in the sample. Recombination of a higher shell electron into the now empty core state creates X-rays imprinted with this atom’s characteristic energy. These X-rays are absorbed by a nearby semiconductor detector, generating electron-hole pairs that are separated and collected as charge pulses.
Fast electronics reliably detect and quantify these pulses, allowing for precise energy spectrum creation. Pulse-processing electronics measure the area under each pulse and then each pulse is “binned” into an energy spectrum. These spectra of characteristic peaks are automatically labeled by the computer.
While EDX is user-friendly and dependable, its limitations include a small analysis volume and poor total X-ray collection efficiency (~1%). To bring about a transformative advancement, a significant increase in the net X-ray count rate, far beyond incremental improvements, was identified as necessary. Addressing this challenge involved exploring all potential avenues for enhancement.
How does EDS work?
When a sample is excited by a source like an electron microscope's electron beam, it dissipates some of the absorbed energy by ejecting a core-shell electron. The ejected electron's place is filled by a higher energy outer-shell electron, and the difference in energy is released as an X-ray. These X-rays carry a unique spectrum corresponding to their atom of origin. EDS spectra are linked to specific sample positions and corresponding elements.
The peak positions in the spectrum indicate the element, while signal intensity reflects its concentration. Integrating an EDS detector with an electron microscope enables atomic-level compositional analysis.
Result quality depends on signal strength and spectrum cleanliness. Signal strength, especially for trace element detection and dose minimization, is contingent on a robust signal-to-noise ratio, enabling faster recording and artifact-free outcomes. Spectrum cleanliness is influenced by the composition of the electron column and affects the presence of unwanted peaks.
Benefits of EDS analysis for materials science
- Sensitive to low concentrations—minimum detection limits below 0.1% in the best cases
- Affords a high degree of relative precision—typically 2–4%
- Non-destructive in most situations
- Usually requires minimal sample preparation effort and time
- Delivers complete analyses of complex samples quickly, often in under a minute
Electroplated bimetallic metal foams imaged with ChemiSEM Technology. Sample courtesy of Prof. Dr. Peter Broekmann, Department of Chemistry and Biochemistry, University of Bern.
EDS analysis instruments
For Research Use Only. Not for use in diagnostic procedures.