Wetting transitions in a binary thin-film

Abstract

The effect of finite thickness of a binary thin-film system exhibiting a consolute critical point on the wetting behavior at the planar film-substrate interface was examined by accounting for the short-range chemical interaction between the film and substrate. Owing to the limited amount of mass available within the film, the first-order adsorption transition obtained from the one-dimensional equilibrium analyses has a physical meaning only when the film is initially uniform in composition. The line of first-order adsorption transition is strongly affected by the finite film thickness, with the composition line shifting inward towards the bulk miscibility gap as the film thickness descreases. However, when the film is initially in a two-phase mixture state, two-dimension simulations showed that the wetting transition from partial to perfect wetting is hardly influenced by the film thickness. The results of the present study suggest that the wetting behavior of a thin film at a given film composition and temperature depends critically on the initial state of the film.