PHYSICAL PROPERTIES OF ULTRA THIN FILMS STUDIED BY X-RAY OPTICAL TECHNIQUES : LANGMUIR-BLODGETT MULTILAYER STRUCTURES, ORGANIC MONOLAYERS ON WATER AND THE SPREADING OF POLYMER MICRO-DROPLETS

摘要

In this paper we show how X-ray optics and in particular X-ray reflectivity at glancing angles can be applied successfully to study very different kinds of physical problems involving ultra thin films. First, we have analyzed the relative contributions of the external interfaces and of the internal structure of a Langmuir-Blodgett multilayer system to the rich interference pattern. Secondly, we have investigated thermally induced capillary waves on a monolayer of behenic acid on water and measured the corresponding roughness as a function of the surface pressure. We observed a strong decrease in the roughness at the liquid condensed to solid phase transition. This significant and striking feature is attributed to the appearence of a bending rigidity in the solid phase. Finally, we have studied the spreading of polymer micro-droplets on well characterized solid surfaces. We have found a very general behavior in which the majority of the polymer volume is contained in a tongue whose thickness is on the order of the molecular lateral size that spreads ahead of the central part. The kinetics and the final stages of the spreading are determined.