Data-reduction procedure for correction of geometric factors in the analysis of specular X-ray reflectivity of small samples

For small samples, the modification of the XRR profile by the geometrical factors manifesting due to profile and size of the beam and the size of the sample is significant. Geometrical factors extend till spill over angle which is often greater than critical angle for small samples. To separate the geometrical factor, it is necessary to know the spill over angle. Since geometrical factor is a smoothly varying function and extends beyond critical angle, it is impossible to determine the spill over angle from XRR profile of small samples. We have shown by comparing the normal XRR profile of a small sample with the XRR profile taken with a surface contact knife edge on the same sample, that the spill over angle can be determined. Thus we have developed a procedure for data reduction for small samples and validated it with suitable experiments. Unlike hitherto used methods which have drawbacks, this is a self consistent method for data reduction