Nanotechnology and model catalysis: The use of photolithography for creating active surfaces

New and very stable model catalysts have been developed. Two types of sampl es on oxidized 4-inch wafers were produced using processes that are general ly employed in semiconductor device technology. A single wafer exhibits 10( 9) to 10(10) active sites on an otherwise flat silicon oxide surface. Sputt er etching of a number of bilayers (Pd/SiO2), stacked on an oxidized Si waf er 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. Act ive material was deposited into the pits by e-beam evaporation or spin-coat ing of precursor solutions. The topography and chemical composition, and th e changes induced by the reaction conditions applied, including stability a nd chemical behavior of the nanostructured systems, were investigated by me ans of AFM, SEM, temperature-programmed methods and XPS.