If the electron beam in an electron microscope hits the specimen surface characteristic X-radiation is generated which can be used for chemical analysis. Mainly, this is done by use of energy dispersive X-ray microanalysis systems (EDS). The detection limit at most is 1000 ppm, and trace elements remain invisible.

If, however, a thin metal foil (target) is placed between the electron beam and the specimen, X-radiation is created within the target which hits the specimen and produces characteristic X-radiation (fluorescence radiation). By measuring this radiation, e.g. by use of the existent EDS, the detection limit is extended to some ten ppm.

The X-ray fluorescence attachment SEMRAY consists of a target holder with five different target materials which is adapted to the particular scanning electron microscope chamber. It is retracable and may be adjusted under vacuum in the three directions in space.

Strong points of the method:

• Detection limit in the range of some ten ppm
  
• Quite easy to operate
  
• No X-ray tubes are required, energy variation by change of the tar-get alone
  
• Sputtering of samples against charge phenomena is not required. This means less time involved, as well as preservation of the sample in its original state (important e.g. for precious samples).
  
• No specific demands on the condition of the sample surface (e.g. rough surface, electron-beam-sensitive specimens).
  
• Qualitatively, the method provides a quality of analysis according to that of standard XRF at a low fraction of the costs of an XRF-instrument.
  

DOWNLOAD: Detailed description of EMSystem's SEMRAY (PDF, 789kB)