Does anybody have an experience with modeling the EDX spectra of thin films in TEM? Is it correct to use the DTSA-II software for these? Faced with the problem in the interpretation of the quantitative results of EDX for specimen with inhomogeneous thickness (for example, 5 nm in thin places and 60 nm in thick ). How critical is the change of thickness to determine the concentration ratio of light and heavy elements in this case?
Samples are amorphous metallic alloys, for example NiW or CoP.
Basically, all elements in this case a well defined EDX. But will the ratio of the peaks of these elements depend on the thickness of the sample, if the difference in their atomic number is high enough and the thickness varies greatly? So problem is do we see real phase separation or it is just wrong EDX quantification related to thickness inhomogeneities?
Dear Vinod! Thank you for your answer! But what do you think about k-factor dependence of sample thickness? there are a number of papers focused on changes in adsorption effect and k-factor with the changes in thickness.. And also, for some materials and thickness(tens of nm), it could be that k-line strongly absorbed.. Please, see this paper for example - doi:10.1016/S0304-3991(99)00082-0. So, in my case I have high roughness in a foil, and in HAADF STEM there is no visible Z contrast, only thickness contrast. And in these modulations of bright and dark contrast correlate with thickness. But EDX shows up to 10 percent difference in W concentration in bright and dark regions, and it is higher in the thinner dark regions... It could be connected with film deposition mechanism, but I also belive that huge thickness inhomogeneities could give their 2 cents...
http://www.sciencedirect.com.sci-hub.org/science/article/pii/S0304399199000820
https://books.google.ru/books?id=_jq8MMfu0bQC&lpg=PA228&ots=BPnAYtD5Mx&dq=EDX%20in%20TEM%20effect%20of%20sample%20thickness&hl=ru&pg=PA229#v=onepage&q=EDX%20in%20TEM%20effect%20of%20sample%20thickness&f=false
It is critical. To be sure not to see thickness effects in XEDS quantification you have to apply the Zeta factor quantification method. I included a poster of EMC Prague about it and recommend to read Williams&Watanabe`s paper about it. With standards of known thickness you can determine the zeta factors for your elements and correct for absorption effects on inhomogeneous thick samples. If the quantification is still wrong channeling can be the root cause. This is due to the effect that in the zone axis the electrons are unevenly distributed in the different atomic columns and the ratio of the xray intensity is proportional to their concentration and the uneven distribution. You can avoid this systematic effect by tilting away from the main zone axis at least 5 deg.By chn aging the high tension you can distinguish between the two effects. Absorption of the xrays stay, channeling will be changed.
Hope this will help
Bert
Dear Bert, thank you very much for your answer and poster! It is very useful info for me
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