Atomic force microscopy of menisci of free-standing smectic films

• DOI: 10.1039/c1sm05285c
• Publication Date: 2011-06-25T08:32:02Z
• Authors: Kirsten Harth; Benjamin Schulz; Christian Bahr; Ralf Stannarius
• Keywords: 02 engineering and technology; 0210 nano-technology

The profile of menisci of freely suspended smectic films is studied by atomic force microscopy and optical interferometry. The measured meniscus profiles show two distinct regions: a circular shape in thicker regions and an almost linear slope near the edge of the planar film area. A macroscopic contact angle of several degrees is found between the meniscus and flat film. In the smectic C phase and in smectic A close to a transition to smectic C, film menisci are decorated by a characteristic stripe pattern that was first described by Meyer and Pershan [Solid State Commun., 1973, 13, 989–992]. We find that the periodically distorted director field of these structures is accompanied by remarkable undulations of the meniscus surface, with height modulations of a few percent of the stripe period. By comparison of detailed features of AFM and polarization microscopy images, we reveal their correlation with the director structures. We collect arguments against the validity of the classical surface splay model.