Hi Michael, On Mon, Jul 7, 2014 at 10:49 AM, Michael Weir <mgw...@udel.edu> wrote:
> Hi Matt and Zhan, > I think this is the point where adding another approach would be very > useful. In my limited experience, XAFS was much more powerful when combined > with other techniques to eliminate potential models. We also needed to use > our "chemical sense". > Oh, yeah, that's absolutely correct. The example was definitely "what Z sensitivity does XAFS alone have?". Zn-Rb and Zn-Ga make absolutely no sense (part of the fun, really!). Zn-Br would be at a very different distance (again, the bond-valence idea). > > Is there a reason you would suspect Se, Ge, Ga, or any of the other > elements in your material? Could you use your beamline to look for these > elements by a quick scan of one of their stronger transitions? If there is > a full coordination shell, detecting the other element this way is > feasible. However, as someone else mentioned recently, dopants would be > much more difficult to detect. > Is there another analytical technique you could use to narrow down the > possible elements in your system? > Yes, just having an XRF spectrum for the sample can probably tell you that many atomic species are not present, which might be obvious but is highly useful. For ZnSe, I think we could confidently conclude that the Ge and As concentrations were something below 10 ppm. Anyway, yes, definitely use "chemical sense", either qualitative (Zn-Rb makes no sense) or quantitative (the As concentration is at least 2 orders of magnitude lower than Se concerntration). --Matt
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