Shirley-Vegh-Salvi-Castle background (or peak-Shirley background)

 

The SVSC-background is a variant of the Shirley-Sherwood background with great advantages since

  • it does not require iterations,
  • it is easier to use,
  • the operator does not require choosing the two points at each side of the spectrum to define the background and,
  • in this way, the fit becomes much less dependent on the operator.
  • Instead of assessing the background employing the whole spectrum (between the two chosen points), the SVSC method assign a background to one or various peaks. This makes complete sense from the physics point of view since the background intensity is not necessarily the same for all the chemical species present in the spectrum. The SVSC method allows for assigning different background intensities to the various peaks. It also permits the use of background parameters obtained from other data. In addition, the quality of the fits is always better.

     

     

    Example

     

    The figure below illustrates the difference between the Shirley-Sherwood and the SVSC backgrounds. It corresponds to a Si 2 p spectrum from a silicon substrate (peak on the right) and an oxide layer (peak on the left). When the Shirley-Sherwood background in employed, the step on the background is shared between the two main features. In the case of the SVSC background, most of the step takes place in the substrate peak. This is because the background parameters employed in the SVSC method were obtained from independent experiments employing pure Si and pure SiO 2 samples. The SVSC background is preferred since the size of the step is conserved as the oxide layer grows. One notable difference is that the Shirley-Sherwood fit suggests the presence of a small amount of signal between the two peaks. This could be erroneously assigned to suboxides peaks.

     



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