Building designed nanostructures in a bottom-up process is a milestone in the development of the nanosciences. It implies to understand and to master the self organization of elementary building blocks such as molecules or nanoparticles. In this perspective, we are studying the self organization properties of preformed, mass selected, metallic clusters deposited on surfaces.
Neutral metallic clusters formed in a gaseous condensation source are deposited on surfaces such as HOPG or more recently semiconductors and oxides. Once the cluster are deposited on the surface, self organization of the clusters in larger nanostructures occurs through a three steps mechanism implying diffusion, nucleation and growth of the nanostructures. The shape of the nanostructures is mostly driven by the competition between diffusion of free clusters on the surface and relaxation of the growing nanostructures. The sensitivity of those two mechanisms to parameters such as mean size of the cluster's distribution, chemical composition of the clusters or deposition rate allows to grow nanostructures exhibiting various shapes, from stable and compact to out of equilibrium and dendritic structures.
Recently, we extended our study to the surface influence on the formation of the nanostructures. Phenomenons such as anisotropic self organization of the nanostructures induced by anisotropic defects of the surface have been observed. In order to further investigate these phenomenons, we chosed to use chemically modified surfaces. Being able to chemically design the cluster / surface interface by chemical modification of quasi model systems such as atomically flat hydrogen terminated silicon (111) surfaces is actually used to get insights of the diffusion / nucleation mechanisms of the deposited clusters. |