Extraction of Signal/Line Intensity in EELS
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For the single scattering spectrum, the overall intensity of the spectrum can be given by,
          I(E) = AE-r + p1σ1(E) + p2σ2(E) + ... + pNσN(E) -------- [1390a]
where,
         p1~ pN -- The probability of scatterings,
         σ1~ σN -- The cross sections from different elements.
         AE-r -- Power-law background fit.

Equation 1390a can be re-written to represent the spectrum as a power-law background and core-loss profile for each edge:
          I(E) = AE-r + C1IC1(E) + C2IC2(E) + ... + CNICN(E) -------- [1390b]
where,
         C1 - CN -- Weightings of the contribution of each element.

The core-loss profiles can be calculated using elemental standards of known thickness and composition. Or, a more accurate way is that the profiles are measured experimentally. In multiple least-squares (MLS) fitting, the weightings of the contribution of each element are adjusted by and their values converted to relative concentrations.

In general, before intensity extraction in EELS analysis, plural scattering should be removed first (see page4352) if the data acquisition is not performed on a thin (<30 nm) TEM specimen.

Different methods have been proposed to extract the intensity of the peaks in an EEL spectrum: [1 - 3]
        i) Take the positive part of the second derivative of the spectrum under the peak. The main advantage of this method is that the measurements are not dependent on background removal, plural scattering and continuous edge contribution.
        ii) Remove the continuous edge contribution and then take the line intensity within an given energy width.
        iii) Take the maximum peak intensity without removing the continuous edge contribution.

 

 

 

 

 

 

 

 

 

 

 

 

 

[1] Riedl T, Gemming T, Wetzig K, Extraction of EELS white-line intesities of manganese compounds: Methods, accuracy and valence sensitivity, Ultramicroscopy, 2006; 106: 284-291.
[2] Kuruta H, Lefevre E, Colliex C, Brydson, Electron-energy-loss near-edge structure in the K-edge spectra of transition-metal oxides, Physical Review B, 1993; 47 (20): 13763-13768.
[3] Kurata H, Colliex C, Electron-energy-loss core-edge structure in manganese oxide, Physical Review B, 1993; 48 (4): 2102-2108.

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