Relative Sensitivity Factors (R.S.F.)

In some instances, different portions of the various core levels (other than those normally used) need to be used for quantification. For example: when overlaps of lines from different species are present it may be necessary to quantify using only the 2p3/2 line instead of the total 2p lineshape. Table 1 presents common relative sensitivity factor (R.S.F.) values derived for CasaXPS based on R.S.F. values used for the Kratos AXIS Supra, Ultra and Nova (this may differ from your instrument - check your library values versus the standard values listed (example: 2p, 3d, 4f, F 1s = 1) before using the derived values (example: 2p3/2, 3d5/2, 4f7/2)). Values that have been derived for specific cases based on standard samples are also presented (example: Mg KLL, Ba for BaTiO3, Eu 3d and U 4f).

To calculate a new R.S.F. for other elements/core lines (for the R.S.F. table type used by the CasaXPS/ Kratos Supra/Ultra/Nova combination) the following formula are used.

RSFp3/2 = RSFp * 2/3

RSFp1/2 = RSFp * 1/3

RSFd5/2 = RSFd * 3/5

RSFd3/2 = RSFd * 2/5

RSFf7/2 = RSFf * 4/7

RSFf5/2 = RSFf * 3/7

Table 1. Relative sensitivity factors for CasaXPS / Kratos Supra  / Ultra / Nova.

a) Use a window of 298-300eV (see Mg link for more details)

b) Calculated from BaTiO3 standard sample

c) New value from standard sample

d) Calculated values based on RSF's from SSX-100 XPS (U 4f = 48.86, Th 4f= 42.75) ratiod to Th 4f from Kratos instruments (Th 4f = 12.75). 48.86/42.75 = RSF(U 4f Kratos)/12.75; RSF(U 4f Kratos) = 14.544. It would be useful if this value could be confirmed with a well characterized UO2 sample.

R.S.F. for Magnesium Auger Line

The CasaXPS/Kratos R.S.F. value (of 0.6) for the Mg KLL Auger line tends to significantly overestimate the amount of magnesium present compared to the quantitative values found from the Mg 2p and Mg 2s lines. A new R.S.F. value calculated from standard samples (magnesium metal and magnesium oxide) has been developed for use on samples where the Mg 2p or Mg 2s peaks are either too small or overlapped with other species. A value of 4.3 +/- 0.3 was found to work quite well. Use a background encompassing the main peak of the Mg KLL line extending from approximately 315 eV to 298-300 eV. Interference from strong C 1s loss structure can be mitigated by shifting the lower binding energy background endpoint to a slightly higher binding energy.

Mg KLL Auger R.S.F. = 4.3 +/- 0.3

Magnesium reference spectra used for this calculation and showing the full Mg Auger peak-set are presented in the link.