Studies of a thin layer by small-angle scattering (SAS) of X-rays in the transmission mode gives weak intensities because the X-ray path is short. Grazingincidence X-ray scattering circumvents this difficulty for the analysis of a thin layer deposited on a substrate or the surface of a bulk sample. Here the X-ray path increases and the background is low enough. The penetration depth can be controlled by controlling the incidence angle of the X-ray beam. The prerequisites of a grazing small-angle X-ray scattering apparatus are a small divergence of the incident beam and a large X-ray flux. The instrument described here consists of a rotating-anode X-ray source, a highly asymmetric monochromator and a position-sensitive detector. The feasibility of grazingincidence experiments is demonstrated with a polished surface of bulk A1-Ag sample. It was possible to perform quantitative measurements of the scattering due to GP (Guinier-Preston) zones in this alloy.

The microstructure of a coating deposited onto a tungsten carbide layer by cathodic sputtering assisted by chemical vapour deposition (CVD) has been analysed by small‐angle scattering of X‐rays (SAXS) with a conventional laboratory set‐up specially adapted for grazing incidence. Anomalous‐scattering measurements have also been performed at LURE, the French synchrotron‐radiation facility at Orsay with the aim of characterizing the structure of phases present in the coating. SAXS results reveal the existence of very small precipitates; the size of these precipitates determined from the use of the Guinier approximation is about 16 Å, the correlation length deduced from the position of the peak in the small‐angle scattering pattern is about 36 Å. The value of the experimental integrated intensity and the variation of the observed intensities with photon energy lead to the conclusion that these nanocrystals are highly enriched in tungsten and embedded in a carbon‐based matrix having a weak electronic density. Electron diffraction results support the assumption of the presence of β‐WC1 −x, an unstable high‐temperature phase. Furthermore, the low electronic density of the matrix is in agreement with face‐centred‐cubic carbon recently proposed in the literature.

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Studies of thin layer by small-angle scattering of X-rays in the transmission mode give weak intensities because the X-ray path is short. Grazing-incidence X-ray scattering circumvents this difficulty for the analysis of a thin layer deposited on a substrate. Furthermore, for a bulk sample, grazing incidence is the only way to study the surface layer, and the penetration depth can be controlled by the incidence angle of the X-ray beam. In this study, we report on krrypton and xenon bubbles which are precipitated in an aluminium single crystal and also in polycristaline deposited layers of metals. These inclusions are produced by ion implantation at room temperature. They are found solid by high-angle diffraction. Comparison between high-angle diffraction and small-angle scattering under grazing incidence lead to a better knowledge of these specific precipitated systems.

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