On the structure of Langmuir-Blodgett superlattices of yttrium and lead stearate alternative bilayers

X-ray reflectivity measurements are used to characterize Langmuir-Blodgett (LB) superlattice composed of different numbers of elementary units. The elementary unit of this superlattice consists of four monolayers of the stearic acid residue which are organized in two different bilayers. One of such bilayers contains yttrium ion in between two stearic residues, and the next one contains lead ion with the same surrounding. The rather large difference between the number of electrons for these metal ions (39 and 82) reveals a sufficient X-ray contrast to receive rather strong Bragg peaks. Positions of these peaks correspond to the tetralayer unit cell (∼100 Å length). For such tetralayer LB superlattices the electron density distribution, namely for one, four and ten unit cells, were calculated.