Lately i have been trying to understand my XPS data for WS2 thin films. The elemental scan i obtained for sulphur was in agreement with the previously reported literature. However, the scan for Tungsten is showing an extra peak(other than expected) as shown in attached file, which i hav'nt been able to figure out.
Dear Pranjala Tiwari,
I think that you misinterpreted the spectra. You have 4 peaks, corresponding to 2 contributions, with spin-orbit splitting (4f 5/2 and 7/2).
I think that your two contributions corresponds to metallic tungsten (the energy should be at 31.6eV) and the one bound with S (the energy should be at 32.4eV). The delta should be equal to 2.17eV.
Regards,
Emile HAYE
Dear Pranjala Tiwari,
I think that you misinterpreted the spectra. You have 4 peaks, corresponding to 2 contributions, with spin-orbit splitting (4f 5/2 and 7/2).
I think that your two contributions corresponds to metallic tungsten (the energy should be at 31.6eV) and the one bound with S (the energy should be at 32.4eV). The delta should be equal to 2.17eV.
Regards,
Emile HAYE
I (partly) agree with Emile that Pranjala has misinterpreted the W XPS data.
Pranjala:
(1) first, you want to make sure that the XPS high-resolution spectrum has been calibrated, as this is a very important first step before you analyse the data;
(2) you may want to have a look at this website http://www.xpsfitting.com/2009/04/tungsten.html, which will hopefully make things about W XPS clear to you;
(3) I did find from the NIST XPS database (https://srdata.nist.gov/xps/EngElmSrchQuery.aspx?EType=PE&CSOpt=Retri_ex_dat&Elm=W) that it has been reported previously that in one case the binding energy of W 4f 7/2 of WS2 was at 31.6 eV. So it make more sense to me if we assign the first peak on the left in the image to be W 4f7/2 in the sulfide form (i.e. WS2) - but again ensure you have calibrated the data! Nevertheless, if someone tells me that W in sulfide form behaves like metallic W - I think I wouldn't be too surprised although I'm not familiar with this sulfide!
(4) With regards to the 'Unknown' and 5p3/2 peaks (the latter of which was incorrectly labelled as the 5p3/2 peak can't be that high), they are probably again 4f/7/2 and 4f/5/2 peaks but contributed from another form of W, possibly WO3 (its 4f7/2 binding energy is slightly over 35 eV)!? This makes sense to me as your WS2 may have been oxidised, depending on how you prepared the sample, for example whether you looked at the fresh surface (e.g. fractured under vacuum) or whether you analysed an area that had been exposed to air (oxygen).
(5) My interpretations above are based on an assumption that this W XPS high-resulution spectrum has been properly calibrated. If you haven't done this, then forget what I said and do calibration right now to see what the positions are after calibration!
Thanks alot for your responses, it was very helpful. I was really looking into my data in a wrong way. I will analyse it again.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films