CHARACTERIZATION OF THE STRUCTURE OF LANGMUIR-BLODGETT-FILMS OF 22-TRICOSENOIC ACID USING X-RAY PHOTOELECTRON-SPECTROSCOPY

The use of variable electron takeoff angles in X-ray photoelectron spectroscopy (XPS) to clarify the deposition behavior and the physical structure of Langmuir-Blodgett (L-B) films is described. The results confirm the Y-type deposition of both monolayer and bilayer films of 22-tricosenoic acid from an aqueous subphase containing cadmium ions onto evaporated films of aluminum on glass. Surprisingly, no cadmium was incorporated in the interfacial layers in either the bilayer or the monolayer. A trapped monolayer of water appears to be present in these interfacial layers. The inelastic mean free path (IMFP) values necessary to model the film structures have been established. These will assist further studies of L-B film structures. The values are 2.7, 2.1, and 2.8 nm for the A1 2s (1410 eV), 0 Is (955 eV), and C Is (1201 eV) photoelectrons, respectively. These are discussed with reference to the previously published values. © 1990, American Chemical Society. All rights reserved.