Complete wetting of a rough surface: An x-ray study

Abstract

The evolution of the surface structure of a wetting film on a rough surface as a function of the film thickness has been studied by x-ray specular reflection and surface diffusion scattering. For thin films (\ensuremath{\lesssim}60 \AA{}) the liquid surface is characterized by static undulations induced by the roughness of the substrate; however, with increasing film thickness the structure is dominated by thermally induced capillary waves. The data are quantitatively described by a model with exclusively van der Waals liquid-substrate interactions.