Surface ordering at the air–nematic interface. Part 2. A spectroscopic ellipsometry study of orientational order |
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| Authors: | Y G J Lau S Klein C J P Newton |
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| Institution: | 1. Institut Laue‐Langevin , 6 Rue Jules Horowitz , BP 156 – 38042 Grenoble, Cedex 9, France;2. H. H. Wills Physics Laboratory , Royal Fort , Tyndall Avenue, Bristol BS8 1TL, United Kingdom;3. Hewlett–Packard Laboratories , Bristol BS34 8QZ, United Kingdom |
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| Abstract: | Spectroscopic ellipsometry has been used to measure enhanced orientational ordering at the nematic–air interface of 8CB as the smectic A phase was approached by cooling from the isotropic phase. The depth profile of the orientational order has been estimated by calculating the ellipsometric parameters for a homeotropic uniaxial surface film on a uniaxial sub‐phase using the Abelès matrix method. This showed that the depth of the enhanced orientationally ordered region was ～10 nm at 0.5°C above the nematic–smectic A transition. This is substantially less than the thickness of the region with surface enhanced smectic order as determined by neutron reflection and a model of the surface structure consistent with both sets of results is proposed. |
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