Your data is very noisy through the edge. Longer acquisition times would help reduce the noise. carlo On Mon, 8 Aug 2016, Siliang Chang wrote:

Hi Carlo,

Thank you for the response. I will try what you mentioned here. The data is taken at APS beamline 5BMD. May I ask what is the effect of longer counting times?

Siliang

-----Original Message----- From: Carlo Segre [mailto:segre@iit.edu] Sent: Monday, August 08, 2016 4:05 PM To: Siliang Chang Cc: ifeffit@millenia.cars.aps.anl.gov Subject: Re: [Ifeffit] Ti data problem

Hi Siliang:

The first thing is that you have misidentified the edge position. Itis way too high in all the data sets.

Put it at the inflection point of the main rise in the absorption curve and you will find that the problem is much reduced.

The second thing is that you have a very bad backgrund problem in your data and, in my estimation your usable data range is no moe than k=2 to k=8. In fact, my suggestion is that you truncate the data by setting the spline range to end at 8. The FT range should probably be set at 2-8 or even 2-7 (somewhere in that range and put a window sill of dk=2 to get rid of some of the ringing.

Once you do those things the data will look much more reasonable.

These data could probably have used some longer counting times. Where did you take the data?

Carlo

On Mon, 8 Aug 2016, Siliang Chang wrote:

...

Dear all,

I am new to XAFS data analysis. I?m currently working on the XAFS data of atomic layer deposited mixed oxide thin film: SnTiOx. I have both Sn and Ti K edge data, and was able to fit Sn edge using a model of (Sn,Ti)O2 solid solution. However, Ti data really confuses me (please see attached file). With Rbkg set to 1, there is a doublet in 1-2 Å region in every data, this is something I have never seen in the literature. I?m wondering if this is normal? Does this mean I should set a larger Rbkg value, say, around 1.5?

I?ve tried to fit the abovementioned Ti data using several models: anatase, rutile, (Sn,Ti)O2 solid solution, perovskite (N is fixed at 6 for all of those), so far no success. I would really appreciate if you can comment on my data processing, any suggestions are welcomed, as I?m new to this, I?m not sure if I?m doing it the right way.

Thank you very much.

Best regards,

Siliang Chang

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org

Hi Jia: For the first one of the spectra, I chose the shoulder in the derivative at 4974 instead of the large peak. I consider the lower energy peak to be a pre-edge feature due to the 3d quadrupole transitions and I generally don't choose that. If the analysis later tells me that I am wrong, I move it accordingly. In this case, the 4974 positoin withthe other parameters I mentioned gives a very reasonable FT. Carlo On Mon, 8 Aug 2016, Qingying Jia wrote:

Hi Carlo,

In many transition metal oxide cases like this, what would be the more proper E0, the position of the apex of the first derivative peak or the second one that is usually higher than the first peak, or it really depends? I have seen people using either. In this particular case, it seems like using E0 of 4967 eV (the first derivative peak position) gives cleaner and more reasonable FT-EXAFS.

Regards, Jia

On Mon, Aug 8, 2016 at 5:05 PM, Carlo Segre wrote:

...

Hi Siliang:

The first thing is that you have misidentified the edge position. Itis way too high in all the data sets.

Put it at the inflection point of the main rise in the absorption curve and you will find that the problem is much reduced.

The second thing is that you have a very bad backgrund problem in your data and, in my estimation your usable data range is no moe than k=2 to k=8. In fact, my suggestion is that you truncate the data by setting the spline range to end at 8. The FT range should probably be set at 2-8 or even 2-7 (somewhere in that range and put a window sill of dk=2 to get rid of some of the ringing.

Once you do those things the data will look much more reasonable.

These data could probably have used some longer counting times. Where did you take the data?

Carlo

On Mon, 8 Aug 2016, Siliang Chang wrote:

Dear all,

...

I am new to XAFS data analysis. I?m currently working on the XAFS data of atomic layer deposited mixed oxide thin film: SnTiOx. I have both Sn and Ti K edge data, and was able to fit Sn edge using a model of (Sn,Ti)O2 solid solution. However, Ti data really confuses me (please see attached file). With Rbkg set to 1, there is a doublet in 1-2 Å region in every data, this is something I have never seen in the literature. I?m wondering if this is normal? Does this mean I should set a larger Rbkg value, say, around 1.5?

I?ve tried to fit the abovementioned Ti data using several models: anatase, rutile, (Sn,Ti)O2 solid solution, perovskite (N is fixed at 6 for all of those), so far no success. I would really appreciate if you can comment on my data processing, any suggestions are welcomed, as I?m new to this, I?m not sure if I?m doing it the right way.

Thank you very much.

Best regards,

Siliang Chang

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Interim Chair, Department of Chemistry Director, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org