At 11:19 18/09/2008, you wrote: >Realy not a good idea, > if you have C on the surface, what C is it ? CO, hydrocarbon, > graphite ? All have a different binding energy of the C 1s ! >I suggest, if youre sample is not to be supposed to contain C, you >should clean it.
This is not my own choice (I am not XPS experimentalist) but what I have read in some XPS papers. The main point: experimental calibration of the binding energy scale requires a reference energy. C1s is surely not the most accurate choice. From discussions with XPS users: this peak is used because, if you don't clean your C free sample, you have C that may originate from contamination in the analysis chamber (vacuum pump oil) and this C is not expected to form chemical bonds with the sample. But as you said in your email you can have other C on the surface and the reference is not expected to be very accurate. >XPS energies have to be calibrated using the Au (or Ag) Fermi energy !!!!! A better choice than C1s but unfortunately not used by all the XPS experimentalists... >and the other question: And for an insulator when the extra 1/2 (or >1) electron goes into the >conduction band and E_F changes....? >An insulater will most probably charge if you do XPS, and the >energies do not tell you much. Can we consider that charge mainly shifts the energy scale? What is the effect on the binding energy differences for a given sample? Pierre