Dear Ravi, what you see is probably the so-called Yoneda peak - it has its origin in the enhancement of the electric field at the surface of the sample if incidence or exit angle in an asymmetric scattering geometry (which you have since you detect the entire scattering pattern with a 2D-detector) are identical to the critical angle of total reflection. It can quantitaviely be calculated in the framework of the dynamic scattering theory (i.e. usually the Distorted Wave Born Approximation, DWBA) - please check the links and the original literature!

A nice summary of XRR and Grazing Incidence small angle scattering (GISAXS):

http://photon-science.desy.de/sites/site_photonscience/content/e62/e189219/e189559/e189883/e189884/e189889/infoboxContent189893/roth_Vorlesung_8_SoSe2011_eng.pdf

Original Paper of Yoneda:

Y. Yoneda Phys. Rev. 131 (1963) 2010, http://dx.doi.org/10.1103/PhysRev.131.2010

Application & theory paper from Jean Daillant

http://www.lps.ens.fr/IMG/pdf/2_JCSFT_96.pdf

Kind regards -Dirk

Below are XRR images showing similar "spots" adjacent to the direct beam for the NIST 2000 SRM. See images below comparing the two thin film samples using Omega-2Theta scans. Note that in the optimized condition when the sample surface is parallel to the incident beam, both the direct beam and the total internal reflection are nearly parallel to each other. They will also remain parallel throughout the Omega-2Theta scan. This feat would have been difficult if not downright impossible using the conventional 0D point counter. I'm curious how you folks achieve this condition with conventional XRD tools. I'd think you'd have to resort to photographic film to determine this condition for each sample prior to XRR measurements/observations. 

Looking forward to your input and comments :-)

https://www.researchgate.net/post/What_is_the_best_way_to_interpret_REAL_TIME_3D_X_Y_o-2TH_o_ph_ch_reciprocal_space_relative_intensity_data_from_HRXRD_rocking_curve_analyses/1

Dear Ravi, what you see is probably the so-called Yoneda peak - it has its origin in the enhancement of the electric field at the surface of the sample if incidence or exit angle in an asymmetric scattering geometry (which you have since you detect the entire scattering pattern with a 2D-detector) are identical to the critical angle of total reflection. It can quantitaviely be calculated in the framework of the dynamic scattering theory (i.e. usually the Distorted Wave Born Approximation, DWBA) - please check the links and the original literature!

A nice summary of XRR and Grazing Incidence small angle scattering (GISAXS):

http://photon-science.desy.de/sites/site_photonscience/content/e62/e189219/e189559/e189883/e189884/e189889/infoboxContent189893/roth_Vorlesung_8_SoSe2011_eng.pdf

Original Paper of Yoneda:

Y. Yoneda Phys. Rev. 131 (1963) 2010, http://dx.doi.org/10.1103/PhysRev.131.2010

Application & theory paper from Jean Daillant

http://www.lps.ens.fr/IMG/pdf/2_JCSFT_96.pdf

Kind regards -Dirk

You are the Man, Dirk! Thanks a million for sharing & opening this awesome "door" to knowledge! We are all embellished and un-afraid of fruits from the "knowledge tree" :-)

• What is the practical implication of these observations?
• What Nano structural parameters could be extracted from such observations?
• How do we take advantage of this in a practical "production/manufacturing" environment since we can quantify it without the help of the Synchrotron?

Dirk! Please feel welcome to post this information for our 2500+ member group in LinkedIn as well (link included). It sounds so much better with your gravitas. If not I'll cut/paste your remarks verbatim later on. Danke! I have a lot to learn yet :-)

https://www.linkedin.com/grp/home?gid=2683600&sort=RECENT

Please check the papers - the intensity of the Yoneda peak is related to the lateral structure of the surface. If you describe by the surface by means of a fractal, you will get the correlation length (distance of peaks of identical height) as well the "jagedness" h - these two factors plus the roghness describe the contour of the surface.  While the correlation length and roughness have a straightforward interpretation, the h-factor is a bit more difficult. Qualitatively speaking, the roughness may have "soft" or "cliff-like" character, which is included in h ranging from 0 to 1. By fitting the measured diffuse X-ray scattering, you may end up with values for the three parameters. See the attached file, which is a compilation of the X-ray scattering from a float glass sample (Hasylab annual report, 2000).

Check it and google for similar studies, there is a wealth of information "hidden" in the 2D-scattering pattern. We are currently investigating the anomalous fine structure in the diffuse scattering to obtain even more information about the atoms in a particular defect site! So work is still going on!

And I thought I was imagining these patterns both in real space (topograph x,y, 2-Theta) and in reciprocal space (rocking curve or Omega/Phi/Chi space) for the past 5 years at least. " :-)

Good news is that I have all the original real time video data from the past 5 years at least. I will analyze all of them again. That'd be fun!

BTW while you are in the "giving mode" and for the purposes of clarity please share with us:

• What is the correct interpretation of the term "diffuse scattering" as it is used in XRD today? Anything other than Bragg? http://x-ray.ucsd.edu/mediawiki/images/6/65/Au_monolayer.pdf
• What is the correct interpretation of the term "rocking curve" as it is used in XRD today? I notice some folks use the term "rocking curve" exclusively for the "Omega only" (decoupled) scan. Is this the convention in the XRD community?

I notice various interpretations of these terms and want to be unequivocal. 

Besides synchrotron based investigations of this phenomenon of Yuneda spots/wings/etc., are you aware of any other references based on conventional laboratory XRD instrumentation in present day literature engaging with this subject? If so, please share.

I'm compiling the original video data in a presentable format. I'll share it soon for your review and analysis!

Here is the first edit. What is your opinion of the music? I'm working on additional annotations and voice over commentary as well. Do remember to click off the Google Ads and mute the audio to reduce distraction. Here is an audio and ad free version: https://www.youtube.com/watch?v=WHQok7cC7vU

https://www.youtube.com/watch?v=4_ZNqnj8xrg

https://www.youtube.com/watch?v=I8lvqjQY7as

Contrast enhanced "Yuneda peaks/spots"! How do we confirm these to be Yuneda spots unequivocally?

Explanation of various pseudo color maps:

Dirk! I printed the material you posted. I'll study thoroughly :-)

New version of video! 

Please note that this XRR data for NIST 2000 SRM with the Bruker D8 was ω-2ϴ "coupled" rocking curve scan. In the XRR data the beam on the RHS of the screen is the diffracted beam which remains fixed on the screen (x,y) while the beam on the LHS is the "incident beam past the sample" and it appears to be moving left. This is so because the detector was rotating counter clockwise, towards the right and away from the transmitted beam (incident beam). Contrast this with the Pt thin film where we are observing the ω only "decoupled RC scan". Here the diffracted beam appears to be translating towards the RHS of the image while the transmitted beam appears to be stationary. The detector was at a fixed zero degree 2ϴ while the sample was rocked counter clockwise about the diffractometer axis through the ω rocking curve range. In the case of Pt thin film XRR data the SDD (sample to detector distance) was about 165mm. At this SDD the 25mm diameter 2D detector would cover roughly 8.7 degrees (+/- 4.35o) 2ϴ.

Do remember to click off "Ads by Google" at the bottom of video and review the rest of the videos in the YouTube "Play List".

https://www.youtube.com/watch?v=wTFOXdFcR_4&list=PL7032E2DAF1F3941F&index=47

I know now that it is slit edge scattering. But why at such low angle of 2-Theta?

I'll post images supporting this notion.