PLANAR NEMATIC ANCHORING ON SIO-COATED SUBSTRATES

The nematic planar anchoring is usually explained by using simple elas tic models: the surface easy axis corresponds to the surface direction that minimizes the excess of nematic elastic energy. When anisotropic rough substrates are used to align nematic liquid crystals, due to th e complex surface morphology, usual elastic models are not directly ap plicable. This paper presents quantitative topographical data of rough substrates, obtained with oblique SiO evaporation under vacuum for ne matic planar anchoring. Experimental data are obtained by means of Ato mic Force Microscopy and they are used to demonstrate the self-affine nature of these substrates and to relate the nematic anchoring with th e anisotropy of the local fractal properties of the substrate itself.