The smectic A-smectic C* phase transition in submicron confined geometry

The influence of confined geometry on the smectic A-smectic C* phase transi tion in the ferroelectric liquid crystal CE8 has been analysed. Using an el ectro-optic response technique, the temperature dependence of elementary ex citations in thin, homogeneously aligned, wedge-type cells of thickness fro m 0.25 to 4 mu m has been measured for different thicknesses of the alignin g layer. In the case of a thin aligning layer (15 nm), we observe in the sm ectic C* phase an increase of the relaxation rate of the phase excitations and a decrease of the phase transition temperature, both of which are propo rtional to the inverse of the cell thickness. For a thick aligning layer (5 0 nm), the relaxation frequency and the transition temperature are proporti onal to the inverse square of the cell thickness. This indicates that the s urface anchoring energy depends on the thickness of the aligning layer. For CE8 on nylon, we obtain a surface anchoring energy W = 10(-4) J m(-2) for a thin aligning layer, and strong anchoring with W greater than or equal to 5 x 10(-4) J m(-2) for a thick aligning layer.