I am studying the adsorption of SO2 on CaCO3 using XPS. Please inform is it necessary to calibrate all the peaks for C1s as my material itself contains C.
XPS is a surface analysis technique and will not give proper quantitative data. I suggest you to use CHNS elemental analyzer. It gives good results for estimation of sulfer.
Thanks Irfan, but I am trying to establish the oxidation state of sulfur. So I am doing XPS. So is there a necessity to do C1s calibration for a sample which has inherent carbon content
Please look attachement with regard to C 1s calibration.
And here - http://srdata.nist.gov/xps/DataDefinition.aspx
According to ASTM standards IT IS the need to perform calibration or at least check it (in the case if You have even dual channel charge neutraliser of dynamic charge neutraliser).
For sure, the two references have to be used - C 1s (not vacuum hydrocarbon) and Ag0 (metal) 3d or wthat so ever.
The need to use the other XPS external standards except C 1s (viz. Au, Ag, ...) is highly preferable if You are examining carbon containing samples. For the explanation of the reason, please, have a look at the attached Table.
Regards,
Dmitry
You can try adding an external standard to material. It can be Au0 4f 7/2 (84 eV), Ag0 3d5/2 (368.3 eV) or Si0 2p (99.4 eV). Of course you can quantify the abosrción. Please review this articles.
https://www.researchgate.net/publication/234082230_Instrument-related_geometrical_factors_affecting_the_intensity_in_XPS_and_ARXPS_experiments
http://www.qro.cinvestav.mx/%7Eaherrera/reportesInternos/arxpsAnalysisSharpIntefaces.pdf
Regards.
Article Instrument-related geometrical factors affecting the intensi...
if you want to be able to compare binding energies to the literature for example, then you should pick a reference point - typically the C(1s) peak. You will possibly have adventitious carbon (~284.8 eV) in addition to a large carbonate peak (~289 - 290 eV) arising from the CaCO3 - therefore use the lower energy peak to calibrate by shifting its energy to say 284.8 if required
If you're stuck without an external standard and you can't resolve the adventitious C peak from the carbonate peak in your C 1s spectrum, then you might consider calibrating to the Ca 2p3/2 feature which occurs at 347.2 eV for CaCO3 (see info and caveats in the link). If you calibrate to Ca, make sure that the carbonate C 1s and O 1s peaks fall at the expected positions before drawing conclusions about the S peak position.
http://xpssimplified.com/elements/calcium.php
The sample surface gets charged while doing XPS characterization. so the data may shift either towards lower or higher binding energy. But you know the general C-C peak which is generally available as an impurity or leftover should give a contribution at 284.8 eV. So you pick your original data and caliberate it according to that. You can check out this video for its details -
https://www.youtube.com/watch?v=AJ-T8uAGsMk
Sachin Kumar The C-C contribution of adventitious carbon at 284.8 eV is a myth. This peak can be anywhere between 283.8 and 286.2 eV depending on the substrate. Correcting the spectrum to the signal from crap that accumulates on the surface does not sound very scientific approach. I know that many people have been doing this for decades but I would be VERY careful trying that.
Here is more info on that:
Article Compromising Science by Ignorant Instrument Calibration-Need...
G. Greczynski Thanks for sharing this article. Could you please elaborate on what would be the correct way of calibrating the XPS spectra other than the Adventitious Carbon?
Sana Mirza - there is no method that works for all samples. The best case scenario is the well-conducting sample with clearly defined Fermi edge that, by definition, marks the "0 eV" point on the BE scale.
In all other cases one has to be very careful. Generally speaking I would always avoid referencing to signals from layers that are not an inherent part of your sample. Here the classical example is the adventitious carbon. The reason being that there is no way to prove that they are in electrical equilibrium with the rest of your sample. The same comment applies also to other techniques like gold evaporation.
We proposed the method based on the sample work function but that works only for samples that are conducting enough to make the work function measurement possible.