Nematic Order Melting on Rough Surfaces Measured by Surface Plasmon Resonance

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

Abstract
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.