Triple-point wetting of van der Waals films on self-affine and mound rough surfaces

The influence of random self-affine and mound substrate roughness on the wetting scenario of adsorbed van der Waals films is investigated as a function of characteristic roughness parameters. The roughness influence, which leads to triple-point wetting, is calculated by the bending free energy penalty of a solid film picking up the substrate morphology. For self-affine roughness, an increment of the roughness exponent H and/or a decrement of the roughness ratio w/xi (with w being the rms roughness amplitude and xi the in-plane correlation length) leads to a noticeable increment of the thickness of adsorbed solid films. Similarly for mound roughness the thickness dependence of the solid wetting layer on the average mound separation lambda and system correlation length zeta follow the general scenario that smoother substrates (w/zeta<<1 and/or w/lambda<<1) lead to thicker solid films. Nevertheless, in this case the thickness increment is a highly nonmonotonic function of zeta and lambda for lambda