Synthesis of monodispersed model catalysts using softlanding cluster deposition
In nanocatalysis, clusters deposited on solid, well-defined surfaces play an important role. For the detection of size effects it is, however, important to prepare samples consisting of deposited clusters of a single size, as their chemical properties change with the exact number of atoms in the cluster. In this paper, the experimental tools are presented to prepare such model systems. The existence of monodispersed clusters is confirmed by various experimental findings. First, the carbonyl formation of deposited Ni-n clusters shows no change in the nuclearity when comparing the size of the deposited clusters with one of the formed carbonyls. Second, scanning tunneling microscopy (STM) studies show that fragmentation of Si-n clusters upon deposition can be excluded. In addition, the adsorption behavior of CO on deposited Pd atoms points to the existence of single atoms on the surface. Furthermore, CO oxidation results on Au-n clusters confirm the existence of monodispersed clusters trapped on well-defined adsorption sites. Finally, we use Monte-Carlo simulations to define the range of clusters and defect densities, for which monodispersed clusters can be expected.