Si/SiO₂-Templated Formation of Ultraflat Metal Surfaces on Glass, Polymer, and Solder Supports: Their Use as Substrates for Self-Assembled Monolayers

This paper describes the use of several methods of template stripping (TS) to produce ultraflat films of silver, gold, palladium, and platinum on both rigid and polymeric mechanical supports: a composite of glass and ultraviolet (UV)-curable adhesive (optical adhesive, OA), solder, a composite of poly(dimethyl siloxane) (PDMS) and OA, and bare OA. Silicon supporting its native oxide layer (Si/SiO2) serves as a template for both mechanical template stripping (mTS), in which the metal film is mechanically cleaved from the template, and chemical template stripping (cTS), in which the film−template composite is immersed in a solution of thiols, and the formation of the SAM on the metal film causes the film to separate from the template. Films formed on all supports have lower root-mean-square (rms) roughness (as measured by atomic force microscopy, AFM) than films used as-deposited (AS-DEP) by electron-beam evaporation. Monolayers of n-dodecanethiolate formed by the mTS and cTS methods are effectively indistinguishable by scanning tunneling microscopy (STM); molecularly resolved images could be obtained using both types of surfaces. The metal surfaces, before being cleaved, are completely protected from contact with the atmosphere. This protection allows metal surfaces intended to support SAMs to be prepared in large batch lots, stored, and then used as needed. Template stripping thus eliminates the requirement for evaporation of the film immediately before use and is a significant extension and simplification of the technology of SAMs and other areas of materials science requiring clean metal surfaces.