electron microscopy
 

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Quantitative X-rays Analysis


If the X-ray spectrum was measured on a TEM, the Cliff-Lorimer ratio technique can be applied for the quantification:

NA/NB = kAB IA/IB

NA,NB: atomic % of element A,B
IA/IB: measured intensity of element A,B
kAB: Cliff-Lorimer factor

The Cliff-Lorimer factor is NOT a constant but depends on the TEM voltage, on the detector efficiency and several other parameters. Thus, accurate results can only be obtained if a standard containing the elements A and B in a well-defined ratio is used to determine kAB. Calculated values of kAB, which are given by the various programs used for X-ray spectroscopy, are only raw approximations and can only be used for quick and rather inaccurate analyses. Although the program output for the composition is a seemingly accurate value with a rather small error bar, the actual error might be much higher because of the kAB problem.
In all cases, the background ("bremsstrahlung") has to be subtracted first. The accuracy of the quantification is additionally reduced by statistical errors of the measurement, absorption, fluorescence, and electron channeling, just to mention the most important effects.

 

Electron-matter interactions
     
ETH Zürich | ETH chemistry department | ETH inorganic chemistry

modified: 6 February, 2015 by F. Krumeich | © ETH Zürich and the authors