Undulation instabilities in the meniscus of smectic membranes

Using optical microscopy, phase shifting interferometry and atomic force microscopy, we demonstrate the existence of undulated structures in the meniscus of ferroelectric smectic-C* films. The meniscus is characterized by a periodic undulation of the smectic-air interface, which manifests itself in a striped pattern. The instability disappears in the untilted smectic-A phase. The modulation amplitude and wavelength both depend on meniscus thickness. We study the temperature evolution of the structure and propose a simple model that accounts for the observed undulations.