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Quantitative Analysis Using LaB6 as an Example

Lanthanum hexaboride (LaB6) is a very illustrative example for quantitative EDS analysis in S/TEM, since it contains two extremes, a very light element (B) and a heavy element (La). LaB6 can be used to show the performance of Bruker's XFlash® detectors and the Cliff-Lorimer quantification routine.

The quantification test of an unknown sample part begins with element identification. Elements to be quantified can be defined by automated or interactive routines. Element lines in the spectrum originating from stray radiation (e.g. Cu from the sample holder) or contamination (e.g. carbon) can be assigned for deconvolution only. The next step is background subtraction. A special physical bremssstrahlung model is provided for perfect fitting. The third step is peak deconvolution, several different fitting models are available for optimum peak separation. Finally, quantification is completed using theoretical or calibrated Cliff-Lorimer factors.

A LaB6 standard (turquoise spectrum in the image gallery) can be used to calibrate the Cliff-Lorimer factors experimentally.

The results using theoretical CL factors already show the excellent performance of Bruker's Cliff-Lorimer quantification. They are very close to the expected composition of 14.29 at.% and 85.71 at.% for La and B, as the tables in the image gallery show. Also, the outcome using the La K series instead of L for quantification shows that the QUANTAX system is well suitable for spectra acquisition and also quantification beyond 20 keV line energy.