INVESTIGATION OF THE INPLANE STRUCTURE OF PB AND NI STEARATE MULTILAYERS BY MEANS OF GRAZING-INCIDENCE X-RAY-DIFFRACTION

Multilayers of fatty acid salts prepared by the Langmuir-Blodgett tech nique on solid supports build structures that are well ordered in grow th direction perpendicular to the surface of the substrate. Open quest ions remain concerning the arrangement of molecules within the layers and their stacking from layer to layer. We have investigated Pb and Ni stearate multilayers on an Si support by means of grazing-incidence d iffraction using X-rays from a synchrotron source. For Pb stearate, si x in-plane Bragg peaks (0 < Q(z) < 3.5 angstrom-1) were detected, wher eas only one peak was found for Ni stearate. The intensity distributio ns along the surface normal (rod scan) were recorded at each Bragg pea k for 0 < Q(z) < 0.24 angstrom-1. Based on the experimental data a str ucture model of the three-dimensional arrangement of molecules within the multilayer domains is proposed which prefers interlayer chain coup ling between neighbouring monolayers.