EDX/WDX (EPMA) X-ray spectroscopy

A scanning electron microscope with EDX detector (energy-dispersive X-ray analysis) and an electron beam micro-probe (EPMA; wavelength-dispersive X-ray analysis) is available for X-ray spectroscopy.

Benefits of both methods:

  • Qualitative and quantitative chemical element analysis
  • All elements except H, He, Be and Li
  • High lateral and vertical resolution (~ 0.5 µm)
  • High absolute accuracy
  • Low detection limit of 0.1 ... 0.01 %
  • Film thickness determination is possible (< 0.5 ... 1 µm

Electron beam scanning makes it possible to record element distribution images (see above). Angled or cross-section polishes are sampled for the measurement of depth profiles. A combined determination of film thickness and composition for thin films (≤ 500 nm) is possible, as well as non-destructive testing by determining the overall mass distribution. Under certain conditions, this even works for 2 or 3-layer systems. Fraunhofer IST has extensive empirical values for the quantitative analysis of materials containing metals in combination with “light” elements (B, C, N, O, F).

Due to its high degree of measuring automation, EPMA is also suitable for the examination of large sample series (50–100 pieces) or for position-dependent measurement (line scans, mappings), for instance in quality assurance or the analysis of defects.

Thin film analysis on dual-layer systems

comparison of measurements using EPMA and an independent RBS (Rutherford backscattering spectroscopy) measurement
© Fraunhofer IST

Non-destructive film thickness determination and simultaneous characterization of the chemical composition of a NiCr/GdTbFe dual-layer film. The comparison of measurements using EPMA and an independent RBS (Rutherford backscattering spectroscopy) measurement reveals the high accuracy for film thickness and composition.

Trace analysis

EMPA trace analysis
© Fraunhofer IST
EPMA linescan over graphitic precipitation in cast iron (left). Cross-section of cast iron with graphitic precipitations (right).

EPMA linescan of a spherical graphite precipitation in cast iron. Detection of 0.13 wt% boron concentration in the particle shell and 0.03 wt% phosphorous in the particle interior. Detection limit typically 0.01 at%. 

Element distribution

EMPA Ni mapping.
© Fraunhofer IST

Mapping of the Ni distribution in a rolled steel sheet over a range of 2x10 mm2. Deviations from the average Ni content of ± 0.4 weight% are shown.