![]() ![]() Obviously, this procedure is just a simplification of the encounter with XPS data and there are many delicate and narrow points to be considered in any individual case. Although all of the points mentioned in the following are not really constrains, but including them in the “procedure” is critical and helps a lot in a clean elaboration of the data. Through a series of experiments (with XPS of Pt and carbon mainly) from which the original question came out and getting engaged with the interpretation of the results, and also using the comments I received here and keeping an eye on the literature, I could refine a sort of “procedure” according to which a reasonable processing of the data and interpretation becomes to a good extent trustworthy. I am back here just to make a sort of conclusion out of all the discussions that might be useful for all. In our case the width was selected to be 1.9 eV. This allows for maximal deconvolution while not losing components because of 'over deconvoluting'. ![]() The width chosen happened to be slightly narrower than those used in curve fitting (see below) the spectrum of interest. In the present case the broadening function was chosen to be a symmetric Voigt function" with 20% Lorentzian character. the convolution of the broadening function and the current deconvoluted spectrum). The most important variable in any deconvolution is the broadening function. The Jansson algorithm implements an iterative type of procedure that can be controlled interactively by a visual evaluation or by monitoring the residual variance between the original data and the reconstructed data (i.e. The backgrounds were removed using a Shirley-type integral and spectral smoothing was carried out using a cubic All data analysis programs (GOOGLY Software) were written in house by A.P. Pretreatment includes background removal and spectral smoothing. I want to ask whether it is acceptable for setting the different but close value for FWHM.įor example, H2O(water) FWHM is 1.6 OH and O2- FWHM are 1.7.Ĭatalysts by XPS using Curve Fitting, Deconvolution and Factor Analysis"-" In order to achieve a successful deconvolution, each spectrum must be pretreated. In my case, I set the same value for FWHM. ![]() Some online information suggests it is better to keep FWHM similar for different peaks. Third Question: Is it necessary to keep FWHM as the same value ?.In NIST, there are six binding energy reference for H2O. The fitted binding energy is a little bit different from the energy in NIST.įor example, H2O, the fitted binding energy is 532.96 eV. Second Question: How to do if the fitted bonding energy is different from the value in NIST XPS database ?Īfter finishing XPS fitting, I compared the fitted bonding energy to the NIST XPS database.įinally, I found the best fitting when the FWHM was 1.7. I gradually changed the FWHM value (from 1 to 2) to found the most suitable fitting condition (concerning physical meaning and fitting residuals). The Lorentzian-Gaussian percentage was fixed as 20 %. The FWHM was set as same value for H2O(water), OH, and O2- peaks. In fitting, I fixed the bonding energy difference as 1.3 eV. First Question: Is my fitting procedure correct ?.The bonding energy difference between them is around 1.1-1.5 eV. In O1s, based on some papers, three peaks should exist (H2O(water), OH, and O2-). Some carbon contamination also contains O, but I neglected the influence of the contamination. Now I want to calculate the ratio of OH to O2. The surface should consists of Al2O3, AlOOH, and Al(OH)3.
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