HIGH-RESOLUTION X-RAY STUDY ON ANOMALOUS DIFFRACTION PEAK SHIFT IN DIMERIZED LANGMUIR-BLODGETT SUPERLATTICE FILMS

Structures of Langmuir-Blodgett (LB) superlattice films formed with alternately deposited fatty acid Cd salts with different alkyl-chain length are studied by high resolution X-ray diffraction method using a synchrotron radiation source. The remarkable diffraction peak shift is observed in the superlattice film. The shift is interpreted in terms of the Guinier effect in partially-disordered superlattice system. Simultaneous modulation of molecular position and of molecular scattering factor results in the peak shift. The effect of alkyl-chain species substitution and of cooling on the peak shift are also described. The partial disorder in the superlattice is caused by dissolution of LB film.