ELLIPSOMETRIC STUDIES ON URANYL ARACHIDATE LANGMUIR-BLODGETT-FILMS

In the presence of counterions, the quality of fatty acid monolayers, prepared by the Langmuir-Blodgett (LB) technique is highly influenced by the subphase pH value. In this paper, we present ellipsometric stud ies on arachidic acid LB films, prepared at different subphase pH valu es, with uranyl (O=U=O)(2+) as the counterion. In order to obtain the refractive indices and thickness, independently, the films were prepar ed as steps with bilayer step size. Refractive index, real and imagina ry part, monolayer thickness and surface roughness on a microscopic an d macroscopic scale have been determined for three different pH values . The results show that films prepared at a pH value of 4.8 and 4.0 ar e of good optical quality, whereas those prepared at pH 2.5 are inhomo geneous. (C) 1997 Elsevier Science S.A.