SPECULAR AND OFF-SPECULAR ANOMALOUS X-RAY-SCATTERING AS QUANTITATIVE STRUCTURAL PROBES OF MULTILAYERS

We have refined experimental techniques and developed theoretical analyses which allow a quantitative structural characterization of multilayers through X-ray diffraction. The use of both specular and off-specular measurements has provided probes of sample structure in the vertical (growth) direction and in the horizontal (parallel to interfaces) direction. In addition, by performing small-angle as well as large-angle diffraction measurements, both mesoscopic and atomic length scales are accessible. The advantages of high intensity and anomalous dispersion available with synchrotron radiation (LURE, Orsay) have greatly contributed to the quality of our data, for which the use of simulation programs has allowed a robust and precise extraction of several structural parameters, such as layer thicknesses, interfacial thicknesses, and interfacial correlation lengths. We have obtained results for a variety of samples, including several Fe/Ir and Mn/Ir superlattices (grown at different temperatures), three Fe/Pd superlattices (having controlled interface profiles), and a monolayer of SiO2 grown on Si through dry oxidation. In this paper we present some representative results. The physical properties of such multilayer materials (e.g. magnetic and transport properties) are generally very dependent on their structural characteristics, in particular their interfacial structures.