[Ifeffit] Ti data problem

[Carlo Segre]

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 at iit.edu]
> Sent: Monday, August 08, 2016 4:05 PM
> To: Siliang Chang <schang37 at uic.edu>
> Cc: ifeffit at 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 at iit.edu   http://phys.iit.edu/~segre   segre at 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 at iit.edu   http://phys.iit.edu/~segre   segre at debian.org