Ahh, it sounds I wasn't entirely clear on what I doing. The measurements were at the In edge, so I aligned all the scans such that the peak in the first derivative of the reference foil was at 27940 eV. The peak of the first derivative in the samples was ~27944 eV. The 1st derivative peaks of samples grown without additional oxygen ("conducting") compared to the samples grown with additional oxygen ("intrinsic") were ~0.5 eV different or less.
Using the peak of the first derivative in Athena for the background subtraction, the refined E0 in Artemis was ~7 eV for conducting samples and ~5.5 eV for intrinsic samples. I also tried setting the E0 in Athena to the peak of the whiteline, which was about 27950 eV. Again the spread between the white line peak values was ~0.5 eV between samples. With this value for the background subtraction in Athena, Artemis refined the E0's to be ~1.5 eV for the conducting samples and ~0 eV for the intrinsic samples.
Another piece of information is that the refined CN's for the samples had an inverse correlation to shift in E0. So the conducting samples with a higher E0 (by 1.5 eV) had a lower CN of about 0.1. The calculated correlation in Artemis for the two variables was ~35%.
I didn't intentionally change anything on the beamline setup. I measured all of the conducting samples and then all of the intrinsic samples. So if there was a sudden change in *something* in between the sample groups, it would be consistent. The sample changes took ~10 minutes at most, so the change would have to happen on that time scale. The only other consistency I noticed is the conducting samples had to be shifted ~0.7 eV to get the metal foil to line up, and the intrinsic samples only had to be shifted about 0.1 eV.
Brandon
2011/6/6 "Dr. Dariusz A. Zając" <kicaj@ifj.edu.pl>
Hi Brandon,
before someone gives you correct answer, could you shortly inform us, what is the E0 for reference foil, for each experimental data. As I understand you have a shift of 7eV between samples, but measured on samples, thus would be nice to see what is the shift for reference.
The second question comes for me automatically - have you done something with the beamline set-up between experiments ?
kicaj
W dniu 11-06-06 08:56, Brandon Reese pisze:_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffitHi all,
I am looking at EXAFS of thin film metal oxides. I am varying both metal content and the oxygen content of the films. I aligned the scans with a metal reference foil collected simultaneously. In Artemis, I have noticed that when changing between films with no extra oxygen versus those with extra oxygen there is a shift in the fitted E0 of ~1.5 eV (after aligning to the foil). I tried setting the E0 in Athena to the peak of the 1st derivative and the peak of the white line with the same result (~7 eV difference). I was a little surprised by the offset because in Athena the E0 values varied by <0.5 eV. I am not sure if the argument could be made that this shift is a result in a changing oxidation state because it doesn't show up in the XANES (at least qualitatively). Are there other experimental effects that could cause a shift like this, or is this likely something real in my material? If anyone want to see a representative group of data, let me know.
I also have an unrelated quick (I think) question on the EXAFS equation. In some references I see a term 1/(k R)^2 and in others it is 1/(k R^2). I couldn't really see any reason for the difference, unless it is to correct for subtle differences in how the other terms are defined.
Thanks
Brandon
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