We present the upgrade and present status of the ultrasmall-angle x-ray scattering ͑USAXS͒ beamline BW4 at the Hamburg Synchrotronstrahlungslabor. In order to extend the accessible scattering vector range, new small-angle setups have been established, making use of the high flux and small divergence of BW4. In standard transmission geometry using a beam size of B = 400 ϫ 400 m 2 ͑horizontalϫ vertical͒, typical small-angle resolution ranges from d max = 90 to 650 nm, depending on sample-to-detector distance. Additionally a new microfocus option has been established. This microfocus option allows reducing the sample size by one order of magnitude. Using parabolic beryllium compound refractive lenses, a new standard beam size of B =65 ϫ 35 m 2 ͑horizontalϫ vertical͒ can be provided. The -SAXS resolution is as high as d max = 150 nm. Using -SAXS in combination with grazing incidence ͑-GISAXS͒ on a standard noble metal gradient multilayer, we prove the feasibility of -GISAXS experiments at a second generation source.

We investigated a gradient of nanometer-sized, self-assembled gold clusters on top of a thin polymer film. Using an advanced characterization method for gradient surfaces and thin films, the characteristic change in cluster height is detected. Our unprecedented approach combining a powerful thin-film characterization method with a micrometer-sized x-ray beam enhances the spatial resolution used thus far by two orders of magnitude. We show that this advanced concept allows for a nondestructive and contact-free reconstruction of the three-dimensional structure and morphology of the nanocluster gradient layer. Despite its change in thickness, the individual clusters’ in-plane shape and distance remains constant.

The adsorption of the ampholytic diblock copolymer poly(methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate) (PMAA-b-PDMAEMA) and the corresponding homopolyelectrolytes of the two blocks, PMAA and PDMAEMA, was investigated from dilute aqueous solution on silicon substrates. The adsorbed amount of polymer as a function of pH, polyampholyte concentration, and salt concentration in solution has been determined by ellipsometry at room temperature. As a function of pH the adsorbed amount reaches its maximum at the isoelectric point of the polyampholyte. Some adsorption takes place even in pH ranges where the surface charge has the same sign as the net charge of the polyampholyte. By variation of the polyampholyte concentration, typical adsorption isotherms were determined at several pH values. With increasing salt concentration the adsorbed amount increases, and above a critical concentration it diverges to very large values. The measured dependencies can be explained by the adsorption of one or the other of the two blocks depending on acidity and ionic strength and are in good agreement with theoretical predictions. Adsorption kinetics has also been studied in detail, and the diffusion coefficient of the polyampholyte toward the surface has been obtained in the early state of adsorption as a function of pH, polyampholyte concentration, and salt concentration.

Within a combinatorial investigation, a gradient sputtered gold layer on top of polystyrene on silicon substrate is addressed. Results from a real-space inspection by transmission electron microscopy are compared with surface-sensitive microbeam grazing incidence small-angle x-ray scattering. The combinatorial approach allows distinguishing different morphologies prepared under exactly the same environmental conditions on one single substrate. The transition of a coalescent layer to an isolated nanoparticle layer is determined as a function of sputter rate. Though optical spectra show only slight differences, the morphology and structure are distinctly different from evaporated layers prepared with same mass thickness.