When doing deconvolution of XPS data, do we need to control the value of FWHM? Does controling the value of FWHM in certain range is right?
Sometimes when im doing deconvolution of C1s peak i controlled it less than 1.6ev FWHM. Other element than C1s i make it less than 2.0ev
Hi Mohamad.
Answering to your question at first lets add a little theory and then continue with a practical application. Full Width at Half Maximum (FWHM) is a full width of a peak (spectroscopic peak) measured at a half of its maximum height. Basically FWHM of an XPS peak (ΔE) can be calculated using the equation:
ΔE2 = ΔE2peak + ΔE2instrum
where ΔEpeak is the natural line width of the XPS peak and ΔEinstrum is the instrumental resolution and is affected by the analyzer pass energy, slit widths and the line width of the incident X-rays. In case of you use microfocusing monochromator, it is likely to get a better resolution then large spot monochromator.
So when fitting the XPS spectra it is always useful to have a reference sample of a pure material measured at your equipment to know the FWHM and possition of the peak. After that you can use this data to fit your spectra. However such FWHM data should be used with carefully as some other features can influence the width of the spectra. Such features can be: naturall line width, rough surface of the sample, chemical interaction, preferable crystalline structure of the surface and crystalline structure of the sample.
Also bear in mind that FWHM for metals are usually less than for oxides, and also that metals can have asymmetric peaks or surface plasmons influencing the shape of the peak.
In case of C 1s peak the FWHM can depend on what kind of material are you measuring, ie. graphite foil, some carbon nanotubes, carbon powder etc. Knowing the FWHM for such pure material without other materials and contaminations, I would tentatively assume to use it as FWHM for spectra deconvolution. In that case I would assume that value of such FWHM in certain range is right.
Kind regards
FWHM stands for full-width-at-half-maximum, i.e it is a measure of the width of the peak. The width is the result of various factors like experimental resolution, life-time broadening as well as it may represent a distribution of different physio-chemical surrounding arround the site from which the signal is originating.
Depending on the purpose of your lineshape fitting it may be a parameter determined in the fit or a constant.
Hi Mohamad.
Answering to your question at first lets add a little theory and then continue with a practical application. Full Width at Half Maximum (FWHM) is a full width of a peak (spectroscopic peak) measured at a half of its maximum height. Basically FWHM of an XPS peak (ΔE) can be calculated using the equation:
ΔE2 = ΔE2peak + ΔE2instrum
where ΔEpeak is the natural line width of the XPS peak and ΔEinstrum is the instrumental resolution and is affected by the analyzer pass energy, slit widths and the line width of the incident X-rays. In case of you use microfocusing monochromator, it is likely to get a better resolution then large spot monochromator.
So when fitting the XPS spectra it is always useful to have a reference sample of a pure material measured at your equipment to know the FWHM and possition of the peak. After that you can use this data to fit your spectra. However such FWHM data should be used with carefully as some other features can influence the width of the spectra. Such features can be: naturall line width, rough surface of the sample, chemical interaction, preferable crystalline structure of the surface and crystalline structure of the sample.
Also bear in mind that FWHM for metals are usually less than for oxides, and also that metals can have asymmetric peaks or surface plasmons influencing the shape of the peak.
In case of C 1s peak the FWHM can depend on what kind of material are you measuring, ie. graphite foil, some carbon nanotubes, carbon powder etc. Knowing the FWHM for such pure material without other materials and contaminations, I would tentatively assume to use it as FWHM for spectra deconvolution. In that case I would assume that value of such FWHM in certain range is right.
Kind regards
http://www.casaxps.com/help_manual/manual_updates/peak_fitting_in_xps.pdf
Please have a look. they discuss it in a detail .
thanks for the answer. Sometimes i find it difficult to do the deconvolution by following a certains range of FWHM value. Because it depends on the intensity of the peaks, pass energy used, physio-chemical charateristic, etc
Full width at half maximum of X-ray peak, to my knowledge, it is used to determine the particle size
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