Nanotechnology and Model Catalysis: The Use of Photolithography for Creating Active Surfaces

Abstract

New and very stable model catalysts have been developed. Two types of samples on oxidized 4-inch wafers were produced using processes that are generally employed in semiconductor device technology. A single wafer exhibits 10⁹ to 10¹⁰ active sites on an otherwise flat silicon oxide surface. Sputter etching of a number of bilayers (Pd/SiO₂), stacked on an oxidized Si wafer surface resulted in billions of isolated towers, consisting of disks of active metal layers, separated by inert substrate material. A second system was produced by etching pits into a heavily oxidized 4-inch Si wafer. Active material was deposited into the pits by e-beam evaporation or spin-coating of precursor solutions. The topography and chemical composition, and the changes induced by the reaction conditions applied, including stability and chemical behavior of the nanostructured systems, were investigated by means of AFM, SEM, temperature-programmed methods and XPS.