I am trying to use UPS to measure work function of MoSe2.
I got two spectra. One is biased during the measurement (-5V) and the other one is non-biased. I am curious about which spectrum I should use to calculate work function.
Many literature used the biased spectrum which can clealy show secondary electron cut-off. the WF is 21.2eV minus the difference between the secondary electron cut-off and fermi level cut-off. But my calculated WF is above 8eV, much larger than reported one.
Other people directly used photon energy minus the intercept of the nonbiased spectrum with the baseline, which is 21.2-16=5.2eV.
Which one should be correct to calculate WF?
You need to use the biased spectrum, otherwise you characterize your spectrometer and not your sample.
However, when I look at your spectra, I am not convinced that you substracted the bias from the kinetic energy before converting to binding energy. That would shift the whole thing towards stronger binding energies and your workfunction would be 4.xeV.
That spectrum looks much better. I learned it the way that you take the middle of the secondaries' cutoff, not the low end, so the work function would be a bit higher.
The cutoff at the low binding energy of course also has a meaning, you can use it to calculate your material's ionization potential, it's
IP= work function + cutoff energy, so that would be 8.xx eV in your case probably.
- Badges
- Science topic
- Similar topics
- Philosophy
- Philosophy Of Science
- Reasoning