Electron microprobe

The electron probe microanalysis (EPMA; . Engl electron probe microanalysis, EPMA, and X -ray microanalysis ) is primarily used for non-destructive analysis of solid surfaces with lateral resolution down to 1 micron.

The principle is based on the wavelength-dispersive analysis (WDS or WDX ) or energy dispersive analysis (EDS, or EDX ) of the light emitted by the sample due to bombardment with an electron beam X-ray radiation characteristic. In this way, elements from atomic number 4 (beryllium ) are detectable. The relative detection limit is 0.01% by weight for the elements, corresponding to an absolute detection limit of 10-14 to 10-15 g. By comparison with known standards, the quantification of the chemical composition is possible because the signal of the characteristic X-ray lines is proportional to the proportion of the respective element. Thus can be taken parallel to the surface image of the element distributions. The obtained information is from a thin surface layer, the analyzed volume per data point is about 0.3 to 3 μm3.

Experimental application

The electron microprobe analysis takes place either by additional detectors in regular electron microscopes (SEM or TEM) or in so-called electron microprobe ( briefly also called microprobe ). The latter are specially equipped for elemental analysis, scanning electron microscopes which are optimized for a higher sample flow, which indeed is undesirable for imaging, but allows a stronger X-ray signal. Electron microprobe are ( usually up to 5 ) in order to map multiple elements simultaneously with the accuracy of the WDS ( mapping ) usually with several WDX spectrometers.