I have XPS data of a metallic and bimetallic sample and I need to interpret its oxidation state and its abundance.
If new to XPS, it is always helpful to start with a standard to use as your baseline. If you have a virgin metallic specimen, start with that and then compare to its oxidized counterpart. 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.
As others have mentioned you will need to use some software package to determine the abundance since relative sensitivity factors vary greatly for different elements. 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. 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. 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.
A spectrum would be helpful here. However, each metallic element will have a certain binding energy value for a specific core electron. As the metallic element is oxidized the binding energy value for the specific core electron will increase.
Please search the NIST XPS database on the internet. From the data base you can check the oxidation states of the elements in your sample. From the binding energy you can get into the periodic table to select the elements and then can find what you want.
good luck!
Thank you for your generous reply. I will interpret them as per you advice
Follow my previous speakers. If available look also for the PHI catalogue. Use a xps peak fit software to find out the oxidation components area (abundance) and position (oxidation state) under your metal peak (check out how was done compensation of a possibly sample charge). Look forward the chemicals shifts with respect to the elemental peak and compare with your peak fit results on the oxidized species.
Last not least; Look for the excellent book of Briggs and Seah: "Practical Surface Analysis" Good Luck!
If new to XPS, it is always helpful to start with a standard to use as your baseline. If you have a virgin metallic specimen, start with that and then compare to its oxidized counterpart. 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.
As others have mentioned you will need to use some software package to determine the abundance since relative sensitivity factors vary greatly for different elements. 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. 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. 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.
Dear Siva,
Please find the attached lecture titled "Characterization of solid catalysts 3. XPS" by
Prof drJ W (Hans) Niemantsverdriet, Schuit Institute of Catalysis
It is a part of his book "Spectroscopy in Catalysis"
Hope this helping
Thanks
Ahmed
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