I am new to using the XPS technique, but will be doing analysis of graphene and graphene oxide. Anyone knows or has any literature on how the calibration is carried out? Also, what master samples are used to calibrate the XPS system for graphene and graphene oxide?
Thanks.
Dear Madam,
for calibration of the energy axis the Au 4f7/2 peak at 83.8 eV is often used as a standard, see e.g.
C.D.Wagner, W.M. Riggs, L.E. Davis, J.F. Moulder, in: G.E. Muilenberg (Ed.), Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Data for Use in X-ray Photoelectron Spectroscopy, Perkin-Elmer Corp, 1979.
Regards, FM
If you have grown the graphene on a Cu-substrate you can use the Cu Fermi edge and Cu 2p as a calibration in situ.
Here are some documentations..
http://onlinelibrary.wiley.com/doi/10.1002/sia.740200309/abstract
https://srdata.nist.gov/xps/DataDefinition.aspx
Thank you for you answers!
The Cu calibration, does it calibrate the source? Or the analyzer? Or both?
The Cu Substrate serves as an bindig energy calibration for the source and the sample.
A calibration for the hemispherical analyzer exists as well?
So, if I use Cu for calibration, then I have to grow graphene on Cu? Or I can grow graphene in its own, then (somehow) load it?
apologies for all these questions, but a lot of reading seems to be not enough!
Graphen can be grown directly on Cu using CVD. As the Graphen film is in direct contact to Cu and by this has the same potential as your analyser the measured bindig energies are referenced to Fermienergy. If you Transfer your sample through air a mild anneal in UHV is reasonable (300°C) for ca 10min. The calibration of the linearity of your analyser is possible with the Cu2p level. Cu2p3/2 (metal) should be at 932.63 eV. Which can be checket with a clean sputtered and annealed Cu sample. If you are in doubt of your spectrometer, check the line position with different pass-energies. If the line is not at the same position for all runs you have to recallibrate the electronics for the voltages at the hemispheres and the gain and offset of the ramp voltage.
Dear C. Pettenkofer,
Many thanks for your detailed answer. My plan is to chemically synthesise graphene and graphene oxide, and hopefully, produce free-standing graphene and graphene oxide films (to eventually be tested in the desalination of sea water) that can be characterised using XPS. In such case, can I still use the Cu2p calibration?
Regards
The Cu calibration was thought as an infernal reference if graphene is prepared directly on Cu. For free standing films you can try to mount your gaphene sample on a gold substrate as Cu will be oxidized and the surface sensitivity is attenuating the 2p level. A clean gold sample is easier to obtain and the 4f level is at high kinetic energies and a very staple reference. For monochramatised XPS you also have the Fermi-level. But Eb of the 4f is the standard reference for XPS calibration.
Dear Christian Pettenkofer,
Many thanks for your answer. I really appreciate.
I am still not sure what reference to use to calibrate the XPS. I will not be using Cu to grow graphene or graphene oxide, so I am guessing (correct me if I am wrong) that either Cu, Au, or Ag can be used for calibration although the graphene or graphene oxide will not be loaded onto one of these metals during the XPS characterisation.
And, also due to this fact, I have another question: if one of the above metals are used for calibration, then what substrate shall I use to load the graphene or graphene oxide onto?
I cannot seem to read this in publications, as only the kind of source and pass energy used are mentioned.
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