Grazing-incidence small-angle scattering. Morphology of deposited clusters and nanostructure of thin films

It is shown that grazing-incidence small-angle X-ray scattering (GISAXS) is a new experimental technique that combines both grazing incidence and scattering at low angles. The experiments are carried out at or near the critical angle: the result is a considerably enhanced surface sensitivity. It allows morphological characterization of aggregates deposited or gathered on a flat substrate, such as silicon wafer or Coming glass. The full potential of this technique is realized when using a synchrotron source (flux, collimation and choice of wavelength in order to avoid fluorescence or to perform anomalous measurements) and when patterns are recorded with two-dimensional detectors: gas detectors or imaging plates (IPs). It is then possible to study the anisotropic shape of the scattering pattern and to determine the sizes of the aggregates. Results are presented for gold clusters deposited on a silicon wafer covered by a carbon sublayer in order to make a comparison with transmission electron microscopy and with scanning probe microscopy. Other examples are presented in order to highlight the advantages of such a technique applied to small inclusions in thin surface layers.