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X-ray spectroscopy in electron microscopy

X-ray spectroscopy can be done in both, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It can be differentiated between energy dispersive X-ray spectroscopy (EDS or EDX) and wave-length dispersive X-ray spectroscopy (WDS). In both cases, X-rays are generated by the interaction of the probe electrons with matter (idealy the sample). In the case of EDS, the detector consists of a Si-based chip (a so called Silicon drift detector) where the energy of the X-rays is converted into a voltage signal proportinate size. In the case of WDS, X-rays are separated by their wavelength (energy) via diffraction on suitable analyse crystals and detected by their diffraction angle.

EDS is typically suited for fast detection as all X-ray energies are aquired at the same time and therefore is the most applied technique in SEM and TEM. WDS is way slower because each diffraction angle needs to be scanned individually. The advantage is a superior energy resolution and lower detection limit in WDS.

more detailed information

EDS-SEM with Oxford Aztec

literature

Oxford Instruments application notes: