Characterization of the local layr structure in ferroelectricliquid crystals using synchrotron X-ray micro-diffraction

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The local layr structure of the broad and narrow wall of a zig-zag defect in a thin-surface stabilized ferroelectric liquid crystal cell was characterized using a synchrotron X-ray microbeam ofless than 5 mum and 1mum spatial resolution. A high precision goniometer using an air bearing system was used. Since the width of the narrow wall is a few mum, the newlydeveloped high precision and high spatial resolution system was quite effective. By using a rocking curve measurement at the narrow wall, the direction of the layr normal depends on the position in the wall and the layr bends in both the w and c direction contrary to the previous plane layr model. The bent layr structure is realized due to the restriction of the constant layr spacing.The local layr structure response to the low electric field was measured at and around the broad wall. Multiple or broad peaks appeared in the rocking curveat the broad wall change into a single and sharp peak when the electricfield is applied to the cell. These observation suggests that the pseudo-bookshelf structure at the broad wall becomes the bookshelf structure with the higher layr perfection owing to the field induced torque on the layrs. The frequency dependence of the rockingcurve profileindicates the relaxation time of the local layr response to the electricfields. It was also observed that the layr imperfection in the S_C phase and S_A phase were related each other. It is concluded that the present method is quite effective to characterize the local layr structure of smectic liquid crystals.