And peak NII becomes three times more narrow then in unpyrolyzed sample. So why there is no peak NIII in unpyrolyzed sample? If one makes peak NII in unpyrolyzed sample of adequate width (being the same as in sample at 800 C), then a third peak NIII must be created to complete a curve fit in the unpyrolyzed sample as well.Īt temperature 900 peak NI becomes twice as wide as it is in unpyrolyzed sample. Curve fit of this spectrum by itself meets all necessary requiremenets of a good curve-fit in which main three peaks are of approximately the same FWHM. Peaks NIII and NIV is added to complete a curve fit. Suddenly peak NII is twice more narrow then it is in unpyrolyzed sample. Peak NI is at the same position of Binding energy and has the same approximate width. Heat treatment of sample at 800C introduces changes which are obvious from the spectral shape. The first sample is unpyrolyzed sample (unmodified) which is used as a reference. Peak NI is of adequate width for N 1s spectral line. Why, suddenly, peak NII is twice as wide as peak NI? Three N 1s spectra for three samples (unmodified and heated at two different temperatures) are analyzed. Let’s look at one example from the literature.
And why spectra on the right represent the “correct” way of curve fitting? What’s wrong with set of spectra shown on the left. So every time I give presentation, which show curve fitting results to people who are not doing it for living, I am talking about physical reasons behind Gaussian-Lorentzian shape of peaks, fundamental limits contributing to FWHM and generals rules of accurate reproducible curve fitting.Īnd the second reason is that even though we all know the rules behind good practices of curve fitting scientific literature is filled with poorly fitted spectra and, therefore, incorrectly interpreted XPS data. Their reaction is that curve fitting is meaningless as we can curve fit any particular spectrum with infinite number of combinations of peaks of different widths and shapes with the same goodness of fit. Why talk about something so well known to the surface analysis community as curve fitting high resolution XPS spectra? Two reasons.įirst is the skepticism I am running into every time I am showing curve fits of spectra to non-surface analysis communities of scientists.
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