Orientational transitions in nematic liquid crystals on substrates with controlled topography

Orientational transitions induced by temperature variation, in cells with n ematic liquid crystal having limiting substrates with controlled topography , are presented. The variable topography was obtained by SiOx deposition in vacuum at an incidence angle around 85 degrees, or by depositions of polyv inyl alcohol (PVA) with different thicknesses, on glasses with the same SiO x deposition. The experimental results are explained by a phenomenological model based on the Landau-de Gennes free energy expansion, taking into account the anisot ropy of the substrate.