Evidence for Capillary Waves on Dewetted Polymer Film Surfaces: A Combined X-ray and Atomic Force Microscopy Study

Surfaces of thin dewetted polyethylene-propylene films were investigated by atomic force microscopy (AFM) and x-ray scattering. The AFM images show the mesoscopic island structure but do not give information about the microscopic roughness of the polymer surface. Together with the AFM data we were able to identify capillary waves on the island surfaces by their specific power laws in the diffuse x-ray scattering signal. The wave number spectrum of these waves is modified by a cutoff introduced by the van der Waals substrate-film interactions.