Profile structures of very thin multilayers by x-ray diffraction using direct and refinement methods of analysis

Meridional x-ray diffraction data from Langmuir-Blodgett multilayers containing two to ten molecular monolayers of arachidic acid were analyzed by two independent methods. A Patterson-function deconvolution technique uniquely provided the electron density profile (8 A{} resolution) of the average, symmetric bilayer repeated in the multilayer. This average bilayer appeared to disorder as the number of bilayers in the multilayer decreased. A refinement technique uniquely provided the profile structure of the multilayer itself; in particular, it could distinguish the individual monolayers in the multilayer. The refinement demonstrated that only one of the monolayers (either the first or the last monolayer in the deposition sequence) in each multilayer was disordered.