Self-seeded nucleation of Cu nanoclusters on Al2O3/Ni3Al(111): an ab initio investigation

The mechanisms of seeding and nucleation of Cu nanoclusters onto an ultrathin alumina template supported on Ni3Al(111) has been investigated by means of ab initio calculations. Single Cu ad-atom diffusion on the oxide film is effective at room temperature, allowing preferential occupation of the defective sites of the so-called "dot'' structure, where the adsorption is much stronger than in the "network'' or any other surface site of the oxide. After the adsorption of the first Cu atom, further nucleation at the "dot'' sites proceeds with the formation of multi-atomic seeds (with up to 6 atoms contained in the defect) that offer stiff anchoring for larger clusters. The whole process is thermodynamically favoured. We therefore clearly confirm and rationalize some experimental evidence showing that the ultrathin Al2O3/Ni3Al(111) is an efficient template for the growth of highly ordered arrays of small Cu nanoparticles.