Fabrication of large-scale ultra-smooth metal surfaces by a replica technique

This paper describes the growth and characterization of large-scale ultra-s mooth metal surfaces produced by an adapted replica technique. Making use o f this method, either amorphous or crystalline masters of different materia ls with ultra-flat surfaces, e.g. mica, glass or polymer coatings on silico n, were coated by a physical vapor deposition (PVD) process with a thin pre cious-metal layer. On the top of this layer a thick Ni surface was grown by electroplating. Both the precious-metal layer and the nickel reinforcement can be stripped off from the master, and the free metal surface that is ma de to appear can be used as a substrate for the self-assembly of molecules, mostly via chemisorption of thiol-functionalized moieties. The use of eith er gold or silver layers led to films exhibiting different morphologies and roughnesses, which are all strongly influenced by the structure of the mas ter's surface and by the conditions during the PVD-coating procedure. Utili zing mica as a master it was possible to grow Ag and Au surfaces made of ul tra-smooth well-defined [111]-oriented crystals. A root mean square roughne ss down to 0.2 nm was measured over micrometer-sized areas by scanning tunn eling microscopy. Very flat An and Ag films have been also produced using t he amorphous masters.