Thin and ultra thin smectic C* films: An X-ray reflectivity study

Publisher Website
Google Scholar
Abstract
We report on X-ray reflectivity studies of thin films of the commercial ferroelectic smectic C mixtures (FELIX 008, Hoechst), prepared by spin coating on various substrates. Upon casting, the films ordered spontaneously with smectic layers parallel to the substrates. This alignment is observed for many different substrates suggesting that it is induced by interactions at the film-air interface. The smectic C phase is maintained even in films of a few smectic layers. However, the smectic-A—smectic-C phase transition temperature, Tc, and the smectic layer spacing are affected by the interfaces and finite size effects. We demonstrate an interesting dynamical effect immediatly after the quenching and the solvent evaporation. The force between the interfaces decay as 1/d3 (d being the film thickness) suggesting a van der Waals (v.d.W) type of force. However, its magnitude and probably the sign are inconsistent with conventional models.