Helium diffraction study of the nucleation and growth of supported metal clusters

A new method for the in situ study of the nucleation and growth of metal clusters on an ionic substrate from vapor beam deposition is presented. It is based on the diffraction of helium atoms from the ionic substrate. From the attenuation of the first order diffraction peak during the growth of metal clusters the nucleation and growth kinetics are obtained. The only additional information needed is the final size distribution of the clusters which can be obtained from transmission electron microscopy. This method has been applied to the nucleation and growth of Pd clusters on MgO (100). With the same method but using the diffraction (specular peak) from the metal clusters it is possible to follow the evolution of the cluster shape during an annealing experiment.