Influence of anchoring strength on focal conic domains in smectic films

We present a study of focal conic domains in smectic-$A$ liquid-crystal films on solid substrates. The antagonistic anchoring conditions of the film surfaces, random planar at the substrate interface and homeotropic at the air interface, enforce the formation of focal conic domains the lateral size of which is dependent on the film thickness. The strength of the planar anchoring on the solid substrate is systematically varied by coating the substrate with special alkoxysilane compounds. For each anchoring strength value, the relation between the size of the focal conic domains and the film thickness is determined. Increasing the planar anchoring strength influences the size-thickness relation and leads to the formation of larger focal conic domains.