Introduction to Wavelength Dispersive Spectrometry (WDS / WDX) in the SEM

Wavelength Dispersive X-ray Spectrometry (WDS / WDX) is a microanalytical technique that measures the same X-ray signal as the more commonly employed Energy Dispersive (EDS) elemental characterisation method on a scanning electron microscope (SEM). However, due to the higher spectral resolution that WDS can achieve, the addition of a WD spectrometer brings some significant advantages; (1) the capability to resolve X-ray peaks that overlap in the EDS spectrum, resulting in more accurate element identification and quantification; (2) higher peak to background ratios and therefore lower detection limits (<100 ppm for many elements). Unlike EDS, which generates a spectrum for the whole possible range of energies instantaneously, WDS measures X-rays of one energy at a time, and therefore is typically slower to produce a result. However, in the AZtecWave software WDS and EDS can be combined to produce results that benefit from the advantages of both techniques – speed, accuracy, and sensitivity.

This tutorial introduces WDS and how it works. It also discusses the advantages of a WD spectrometer with a Rowland circle geometry and fully focussing crystals, as found on electron microprobes (i.e., EPMA) and the Wave spectrometer integrated with AZtecWave. Real-world applications examples, and results obtained using SEM based WDS and EDS are presented throughout.

You will learn:

• The principles of Wavelength Dispersive Spectrometry (WDS/WDX)
• How the Oxford Instruments Wave spectrometer works and how it enhances a SEM-EDS system
• When you might want to conduct WDS analysis and typical applications