AFM EXPERIMENTAL-OBSERVATION AND FRACTAL CHARACTERIZATION OF AN SIO-COATED PLATE FOR NEMATIC BISTABLE ANCHORING

We observe with an atomic force microscope (AFM) the surface of a roug h substrate that gives bistable anchoring for typical nematic liquid c rystals. This surface is obtained by oblique evaporation of a thin fil m of SiO (average thickness approximately 150 angstrom) on a smooth gl ass plate. It appears highly disordered and exhibits very small struct ures with a typical horizontal size of 500 angstrom and a typical vert ical size of 200 angstrom. The fractal properties of the AFM data acqu ired indicate that the growth process of the substrate SiO structures is governed by a diffusion law. It is reasonable to expect a decrease of the surface order parameter for the interface layer of a liquid cry stal close to this kind of substrate.