LOCALIZATION OF A MAGNESIUM DELTA-SHEET WITHIN A LEAD STEARATE LANGMUIR-BLODGETT MULTILAYER BY X-RAY REFLECTIVITY MEASUREMENT

Lead stearate multilayers have been prepared by Langmuir-Blodgett deposition where one lead layer has been replaced by magnesium at variable positions. The position of a Mg sheet within a lead stearate sandwich is determined by small angle X-ray scattering (SAXS) experiments. We find that the ionic layers closest to the substrate and the air modulate the phases of the scattering amplitudes in a characteristic way. Especially, the region between the first and second Bragg peak allows evaluation of the sequence of Pb and Mg layers unambigously. Additionally, the exact position of the Mg layer within the sandwich can be determined with atomic resolution, if Mg is positioned at the top or bottom of the multilayer. For intermediate positions, the accuracy is up to 3 times smaller.