Energy dispersive X-ray spectroscopy - Definition and Overview

The energy dispersive X-ray spectroscopy (EDX or EDS) is a method used to determine the energy spectrum of X-ray radiation. It is mainly used in chemical analysis, in a X-ray fluorescence spectrometer (especially portable devices), or in an electron microprobe (e.g. inside an scanning electron microscope).

The detector is a semiconductor, usually silicon doped with lithium (Si(Li) detctor). The semiconductor is polarised with a high voltage; when a X-ray photon hits the detector, it creates electron-hole pairs that drift due to the high voltage. The electric charge is collected, it is like charging a condensator; the increment of voltage of the condensator is proportional to the energy of the photon, it is thus possible to determine the energy spectrum. The condensator voltage is reset regularly to avoid saturation.

To reduce the electronic noise, the detector is cooled by Peltier effect or best by liquid nitrogen.

See also

• Wavelength dispersive X-ray spectroscopy