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

利用空间分辨率分别小于5 μ m和1 μ m的同步x射线微束，研究了薄表面稳定铁电液晶电池中锯齿状缺陷宽壁和窄壁的局部层结构。采用空气轴承系统的高精度测角仪。由于窄壁的宽度很少，因此新开发的高精度、高空间分辨率系统是非常有效的。通过在窄壁处的摇摆曲线测量，层法线的方向取决于在壁中的位置，与之前的平面层模型相反，层在w和c方向上都弯曲。由于层间距不变的限制，实现了弯曲层结构。在宽壁处和宽壁周围测量了局部层结构对低电场的响应。当电场作用于细胞时，摇摆曲线上出现多个或宽的峰，宽壁变成一个单一的尖峰。这些观测结果表明，宽壁上的伪书架结构由于层上的场感应转矩而成为层完善度较高的书架结构。岩石曲线的频率依赖性表明了局部层对电场响应的弛豫时间。同时观察到S_C相和S_A相的层缺陷是相互关联的。结果表明，该方法对近晶液晶的局部层状结构的表征是非常有效的。

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.