electronprobeEPMAanalyse

Electron probe microanalysis (EPMA), also known as electron probe analysis, is a microanalytical technique that uses a finely focused electron beam to excite X-rays from a specimen. The emitted characteristic X-rays are measured to determine the elemental composition at small, user-defined areas, typically down to a few micrometers in diameter.

Modern EPMA instruments combine a field emission or tungsten electron column with detectors for X-ray spectra. Most systems use wavelength-dispersive spectrometers (WDS) for high-resolution, quantitative analysis and/or energy-dispersive spectrometers (EDS) for rapid qualitative screening. The beam energies are typically 10-30 keV, with currents adjusted to balance signal and sample damage. Sample preparation may require polishing and conductive coating for non-conductive materials.

Quantitative results require calibration against standards and corrections for atomic number, absorption and fluorescence (the ZAF corrections) or other matrix correction methods. EPMA can quantify major elements and trace elements down to tens of parts per million, depending on instrument, material, and measurement conditions. Element maps and line scans can be produced to reveal distribution within a study area.

Applications span geology and mineralogy, metallurgy and materials science, semiconductor device analysis, and cultural heritage conservation. The technique is well suited to minerals and metals but requires conductive or coated samples and careful avoidance of beam-induced damage and charging for insulators. Limitations include spatial resolution limited by beam diameter and the need for standards for accurate quantification.

EPMA emerged in the mid-20th century and has since become a standard tool in analytical laboratories, evolving from early single-detector systems to modern multi-crystal WDS and silicon drift detectors. It provides robust, quantitative elemental data in a non-destructive manner on small sample areas.