J. Phys. II France
Volume 6, Numéro 2, February 1996
Page(s) 205 - 214
DOI: 10.1051/jp2:1996177
J. Phys. II France 6 (1996) 205-214

Nematic Order Melting on Rough Surfaces Measured by Surface Plasmon Resonance

J. Papánek1 and Ph. Martinot-Lagarde2

1  Department of Optics, Komensky University, Mlynska dolina F2, 84215 Bratislava, Slovakia
2  Laboratoire de Physique des Solides, Bât. 510, Centre Universitaire, 91405 Orsay Cedex, France

(Received 9 June 1995, received in final form 18 October 1995, accepted 7 November 1995)

Our measurements by a plasmon technique show that the structure of grazing incidence (85°) evaporated SiO x thin films is highly porous. A large fraction of the voids is open and can be penetrated by a nematic liquid crystal put into contact with the SiO x layer. The nematic material in the voids remains disordered (isotropic) in the whole nematic range. This indicates that the director orientation in the volume of the liquid crystal must, at least in this case, be determined by other mechanisms than the ordering of molecules in the grooves of the rough surface. Further, we have found a transition region where the order parameter gradually decreases from the bulk value to zero (disorder) at the surface with a coherence length of approximately 8 nm.

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