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Surface ordering at the air-nematic interface. Part 2: a spectroscopic ellipsometry study of orientational order
Lau, Y.G.J.; Klein, Susanne; Newton Christopher J.P.; Richardson, Robert, M.
Keyword(s): order parameter; air-nematic interface; ellipsometry
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 subphase using the Abeles matrix method. This showed that the depth of the enhanced orientationally ordered region was ~ 10nm 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. Publication Info: Liquid Crystals
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