I know ionization potential can be obtained by adding the work function to the valence band maximum, which can be both determined directly from a UPS/XPS spectra. I was wondering if this is possible for ionization potential to be determined or its position shown on the spectra?
I would also appreciate a reference with this description.
The ionization potential is usually only determined by UPS. XPS does not give you good information since the cross section at the onset of the DOS close to the Fermi level is rather low, the energy resolution much worse than in UPS and I am not sure if the cutoff for low kinetic energy electrons is observable in the background (these are the electrons that make it barely above the vacuum level and therefore give information on the work function).
In the UPS spectra the Ionization potential does not show "directly". It is the difference between the excitation energy and the width of the spectra as shown in the picture below. This is equivalent to calculating it as IP=21.22eV-cutoff position+valence band onset. Since the work function is WF=21.22eV-cutoff position this is again equivalent to what you said in your first sentence.
The ionization potential is usually only determined by UPS. XPS does not give you good information since the cross section at the onset of the DOS close to the Fermi level is rather low, the energy resolution much worse than in UPS and I am not sure if the cutoff for low kinetic energy electrons is observable in the background (these are the electrons that make it barely above the vacuum level and therefore give information on the work function).
In the UPS spectra the Ionization potential does not show "directly". It is the difference between the excitation energy and the width of the spectra as shown in the picture below. This is equivalent to calculating it as IP=21.22eV-cutoff position+valence band onset. Since the work function is WF=21.22eV-cutoff position this is again equivalent to what you said in your first sentence.
Thank you Selina for the response. Could you please suggest some good references for PES methods especially UPS?
Unfortunately, I don't know of any really good book on UPS, you could read "Photoelectron Spectroscopy" by Hüfner, but it is quite extensive and less helpful for experimental issues. My suggestion: look for some PhD thesis on the topic of UPS in combination with whatever your topic is (just google it). Often you find very good descriptions in these.
Thank you. I have also downloaded your thesis for further reference. I hope you won't mind.
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