Microbeam grazing incidence small angle X-ray scattering - A new method to investigate heterogeneous thin films and multilayers

The combination of the ID13/ESRF micrometer-sized X-ray beam with the reflection geometry allowed to establish a new scattering method for investigating laterally patterned heterogeneous multilayers and interfaces. This new method - called microbeam grazing incidence small angle X-ray scattering (μGISAXS) - has been applied to a novel gradient multilayer of self-assembled nanometer-sized noble metal clusters on top of a polymer layer, being of significant importance for many technological applications, including biorecognitive sensoring. The new feature of using a 5 μm X-ray beam allows to characterize laterally heterogeneous samples on two length scales, induced by the small beamsize and reciprocal space resolution. From the two-dimensional μGISAXS patterns the three-dimensional structure and morphology of the gradient of gold (Au) clusters was reconstructed using detailed model simulations. Though being a highly complex sample, it turned out that the gradient is characterized by a single parameter, namely the cluster height. Atomic force microscopy (AFM) and optical absorption spectra provide supplementary information and help to enlighten the structure of evaporated gold clusters on polymer layers.