Thickness dependence of the glass-liquid crystal buried interface structure

We have used Grazing Incidence X-ray Diffraction (GIXS) to study the struct ure of a smectic A liquid crystal (LC) at the buried LC-glass interface in liquid crystal films. This measurement is done in reflection mode through t he glass substrate, which consists of a grating photolithographed onto a 0. 2 mm thick slide. The observed in-plane alignment indicates the presence of tilted layers within 50 Angstrom of the glass interface, inside the groove s. These layers correspond to the tilted region observed previously in samp les confined within the grating grooves. The tilted layer region is suppres sed by the grating induced homogeneously aligned LC layers, which act as a new confining boundary that modifies the LC structure within the grooves. T he interaction between the two observed in-plane regions depends on the thi ckness of the LC films as well as the depth of the gratings' grooves.