Studies of thin smectic C films by X-ray reflectivity |
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Authors: | O Marinov E Olbrich G Cohen I Entin D Davidov |
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Institution: | Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel |
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Abstract: | The smectic order in thin and ultra thin films (150–600Å) of the chiral ferroelectric liquid crystal mixture ZLI-3654 is studied using the X-ray reflectivity technique. The spin cast films on various substrates (float glass, Si wafer, polymer coated glass, etc.) order spontaneously with smectic layering parallel to the substrate surface. A simple model which assumes a sinusoidal density modulation can describe well the experimental reflectivity profiles. The X-ray reflectivity provides a method to evaluate the phases of the structure factor. We demonstrate, for the first time, that is possible to extract the molecular tilt angle, , in ferroelectric liquid crystals from X-ray reflectivity measurements of ultra thin films. The temperature dependence of the tilt angle in the smectic C* phase are almost independent of the film thickness (down to 200 Å) and are similar to those in the bulk. |
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