Dear All,
I am using CasaXPS to fit the O1s region of my reduced graphene oxide sample. I am expecting to see 3 peaks :
C-OH
C-O-C
O=C-OH
should I use the same line shape and fix the FWHM to fit all the 3 components ? or should I allow the FWHM to change from one component to another ?
Also, how do I know if my fitting is physically meaningful ? other than just having residual STD below 1.
The peak width is essentially a "machine constant" so, yes, it should be constant or have at least little variation. Here is a good reference that shows a well-executed deconvolution which was an important reference for my own PhD work:
Article Initial Stages of Oxidation on Graphitic Surfaces: Photoemis...
"The peak width is essentially a "machine constant" so, yes, it should be constant or have at least little variation."
While this might be more or less correct in your case here, this is not generally true. Peak width is a combination of setup resolution (machine constant) and natural line width (dependent on the lifetime of the core hole). For example, the peak width of metal oxides is often much larger than the corresponding pure metal peaks.
Thorsten Schultz Good point, I kinda lost track of the natural line width since I rarely looked at stuff grown on metal with XPS. But as you said yourself, in this case that doesn't make a difference.
A first approximation would be to keep the FWHM the same, however if one particular species has perhaps more vibgrational modes, then these can broaden the FWHM (a common example of this are OH groups on transition metal oxides vs the metal-oxygen bonds)
Any fitting you need to cross reference with another core-level - in this case your C(1s) envelope to confirm thsoe groups are present and your fitting makes sense numercially.
See for example the logic I set out in the following paper:
Article Comments on the XPS Analysis of Carbon Materials
Thanks gentlemen for your insights. I really appreciate all of your answers. a special thanks to David J. Morgan as his paper addresses exactly what I was looking for.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Carbon Materials
- Graphite