Étude structurale de nanomatériaux par diffraction X : utilisation d'un montage avec optique multicouche à collimation 2D

Abstract
We present X-ray diffraction measurements from an experimental setup based on a two-dimensionally collimating optical element. This device consists of a parabolically bent W/Si multilayer (ML) with laterally graded period. Hence, with only one reflection, divergent X-rays from laboratory sources are converted into a nearly parallel beam. We focus on the possibility to use such an optic for the fine structural characterization of nanomaterials. A 4 nm thick epitaxial film of Tb(0001) deposited onto Al₂O₃(111) substrate was used as a test -sample. Although a large gain of photons with the ML optic is obtained in comparison with a setup using a flat graphite crystal as primary monochromator, the presence of high parasitic contributions (Cu K, W L radiations,) prevents from a fine analysis of the diffraction diagram. In order to overcome this effect we also made comparative tests using different analyzers. In particular the adjunction of a Ge(111) analyzer crystal led to a very good peak to background ratio suitable for the measurement of nanomaterials.