Hi all.
Brand new to XRR and have no sense of what is good data, bad data, and what required post-processing steps are needed before modeling the data.
I am only using XRR to obtain density and have no interest in interfacial/surface roughness, thickness, or any other information that may be gleaned from XRR analysis. Have read some about geometrical corrections, subtracting diffuse profiles (I have not obtained).
I'm attaching a scan that I'm currently working through. Hoping to just get some basic insight into whether the scan itself is usable, and if any corrections (geometric/diffuse scans) are even needed if I only want the critical angle. Any links to XRR analysis reviews would be much appreciated.
Due to geometric factors from beam profile, beam size, and sample size, microscopic samples have dramatically changed X-ray reflectivity (XRR) profiles. Geometric factors raise the spill-over angle, which sometimes surpasses the critical angle for small samples. To separate geometric components, know the spill-over angle. The XRR profile of microscopic samples cannot determine the spill-over angle because geometric characteristics smoothly vary and extend beyond the crucial angle. Comparing the normal X-ray reflectivity (XRR) profile of a tiny sample to a surface-contact knife edge profile on the same sample may estimate the spill-over angle. A technique has been developed to compress tiny sample data and verify it using testing. Unlike limited techniques, this data reduction strategy is self-consistent.@Sean Clark
Dear Sean Clark ,
in my opinon the spill-over angle will not produce a cut-off but only a kink in the reflectivity profile.
The total reflection cut-off is clearly seen here in your diagram at the critical angle of total reflection as a sudden drop down of the reflectivity. Fortunately this cut-off is quite sharp so that the critical angle (here in your diagram labelled as the magnitude of the critical momentum transfer vector qc) can be well identified by eye, being just at the beginning of the drop down of the reflectivity.
For samples having larger optical constant ß (ß being proportional to the x-ray attenuation) compared to your carbon film, we will have the situation that there will be no sharp cut-off*). In such cases one has to fit the reflectivity R(q) with respect to the optical constants delta and beta of the x-ray refractive index. From a known delta you have access to the density.
But as Pradeep Duraiyarasan mentioned, here the spill-over angle will play a role and one has to model the reflectivity curve accordingly.
You may also have a look at my answer given in :
https://www.researchgate.net/post/How_to_determine_density_of_a_film_using_XRR_techniques
*) please have a look at most right set of curves in the attachment
This diagram was taken from my diploma thesis (1977)
Best regards
G.M.
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