Hello everyone,
As we know, in X-ray Photoelectron Spectroscopy (XPS), we collect spectra for a sample using one of several X-ray sources, such as Mg, Al, Ag, or Cr. Sometimes, we encounter an overlap between an Auger line and a photoelectron line in the spectra. To resolve this, we can switch to another X-ray source to shift the Auger peak. My question is: wouldn't this influence the information we obtain from the spectra?
I believe that this does not cause any misinformation about your sample because we are using XPS, not Auger Electron Spectroscopy (AES). What's your take on this? I'm looking forward to your insights and thank you in advance for your answers!
When you change the excitation wavelength, you change the cross sections and thus sensitivity for the corresponding photoelectron emission energies.
So if you're thinking about e.g. switching between Mg and Al excitation which would be the most common in XPS, you can check cross section tables, e.g. the classical Scofield or Yeh/Lindau tables, whether the line you're interested in would loose sensitivity in a substantial manner.
If these do not indicate that you would run into difficulties, switching the emitter metalfor better separation between your desired emission bands and the Auger bands definitely makes sense.
Jürgen Weippert Thank you for your answer. It occurred to me as well that Auger peaks could also be relevant. However, if I were to shift the Auger peaks using a switching source (as mentioned in the following article on page 9), resulting in Auger peaks appearing at different binding energies (or kinetic energies), wouldn't this alter the significance of these peaks? I've been considering that since XPS primarily focuses on photoelectron lines, unlike AES, perhaps that's why the impact of shifting the binding energy of Auger peaks was overlooked. What are your thoughts?
Article Introduction to x-ray photoelectron spectroscopy
For Auger peaks, the kinetic energy is the characteristic parameter due to the electron emission mechanism.
When you change the excitation energy, photoemission bands will appear at constant binding energies, but the kinetic energy will shift linearly.
Auger electrons, as they are formed in a multi-step formation mechanism, will always have the same kinetic energy, so if you recalculate to binding energy, it will look like they "shifted".
Bonding information in the sense of a chemical shift would not be affected by that, if that's what you mean by "significance".
Dear Irin Naher, You might also consider the effect of changing probing depth when changing photon energies, i.e., surface sensitivity or bulk homogeneity (e.g. layered materials). For example, if you go from Mg to Cr, where Mg would be much more surface sensitive than Cr.
John Åhlund Thanks for pointing that out. Yes, some sources are more surface sensitive than others. At the same time some elements are more source sensitive than others.
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