This should be done cautiously, but valuable information can be gained especially if you can analyze the relative growth/decrease of the two peaks in-situ while the sample oxidizes, for example. However, this being said, it is reasonable to compare the relative raw intensities of two peaks if they are in the same energy range (separated by a couple eV), such as your metal and its oxide. For example, this means that although the raw intensity of the O1s peak may be larger than the C1s peak, there could in fact be more C than O because oxygen produces more photoelectrons than carbon. By doing so, and ensuring nothing else is different or has changed between the two samples, you can determine the exact binding energy of the metallic oxide.Īs others have mentioned you will need to use some software package to determine the abundance since relative sensitivity factors vary greatly for different elements. If you have a virgin metallic specimen, start with that and then compare to its oxidized counterpart. However, probably the best is the one that is provided with your instrument.If new to XPS, it is always helpful to start with a standard to use as your baseline. This is not a free program but it is powerful and can be used for other spectrocopic methods.Īnother program used is Unifit and this one is free. I might bluntly suggest that it in your ending sentence is. Different shapes means more parameters to fit… With too many parameters, the result can be biased by the user.Īmong the softwares used (besides classical peakfit programs like PeakFit, Igor, Origin…) for XPS the most common software used is CasaXPS. CASA is a well-respected, broadly-used, extremely powerful software application for XPS analysis. In the old days we used Gaussian but nowadays pseudo-Voigt shapes are commonly used. Of the two, peak shape is tough to solve. There are two problems in spectroscopy data fitting procedures : baseline and peak shape. Now, after this warning – and remember the Poisson distribution means that if you want data with a signal/noise ratios 10 times better … you need to acquire 100 times longer- the fitting software of the instruments is in general good. Contrary to what have you seen in recent Hollywood movies – where from a poor low resolution video, a smart tech person after 400 % zoom, does some fancy data enhancement procedure in order to see the face of the criminal- zooming and data treatement of poor data does nothing more than add to the noise. There is no way you can get good fit with bad data (data is bad either because the acquisition conditions were not adequate or, worse, because the sample was bad). Before going into detail about fitting softwares, let me remind you a sound principle : the fitting results can be as good as the data is. There are several good software for fitting XPS data.
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January 2023
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