Can anybody tell me how to get a SE cutoff value from UPS?
I read some papers about how to calculate the VBM; but i am not sure which one is correct. For my figure, how to get a VBM?
OK, two things:
1) Did you apply a separating bias to the sample? That's a prerequisite in order to have useful data since you need to differentiate between spectrometer and sample secondaries. Your data looks more like that of an unbiased sample since 3.9-4.0 eV is a typical order of magnitude for a semiconductor workfunction.
2) Regarding the actual cutoff determination: we usually used the middle of the secondary electron edge (thus interpretating lower energies as broadening) as the cutoff value, but in our samples the cutoff was usually sharper than the one shown here so a base point interpretation wouldn't have made a difference for the first decimal.
Dear Mr. Weippert,
Thanks for your kind explanation. That gives me a great help.
The sample was applied with a -5 V separating bias. And I have deducted it.
I am sorry, I have two more questions. Can I get the workfunction is ~3.9 eV?
secondly, Can I get the VBM from this fingure?
Thank you for your kind patience.
Jürgen Weippert
OK, so you applied a -5V bias and subtracted it already from the kinetic energy? That was important to know.
In that case you can actually say that your work function is ca. 3.9eV, yes.
And also yes, you can determine the valence band maximum here.
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