Determination of micrometer length scales with an X-ray reflection ultra small-angle scattering set-up

We show that the accessible range of length scales of structures deduced with ultra small-angle scattering (USAX) experiments can be enlarged by more than one order of magnitude in reflection geometry set-ups. From the analysis of the diffuse scattering without further model assumptions the length scale of the structures is determinable. The method is illustrated by an example of thin blend films of deuterated polystyrene (dPS) and poly-paramethylstyrene (PpMS) where um-structures are recovered. The results are compared to atomic-force microscopy measurements. For a further comparison, USAX data of a water-based dispersion of polymer particles are presented. They illustrate the resolvable length scale of the conventional transmission geometry.