Tuneable rough surfaces: A new approach for elaboration of superhydrophobic films

The present paper describes the process enabling the production of superhydrophobic surfaces by tailoring their surface topography and chemical properties. These surfaces have been developed using a simple plasma based techniques combining plasma etching and plasma polymerization on silicon substrates. These techniques have been chosen because they provide features such as large area processing and high reproducibility. The key step of this process is the modification of the surface topography of the substrate to create high roughness before deposition of fluorocarbon coating. The roughness on silicon wafer is induced by the over-etching of a photoresist layer by a SF6 plasma treatment. The different layers obtained exhibit contact angles from 102 degrees up to 180 degrees depending of the preparation conditions. The observations of the topology by scanning electron microscopy reveal that the presence of dendrites on the surface of the substrate favors the superhydrophobicity of the films. The variations of the contact angle have been explained using the Wenzel's or Cassie's models. (c) 2005 Elsevier B.V. All rights reserved.