Correlated jumps in small metallic island diffusion.

J. FERRÓN, L. GÓMEZ, R. MIRANDA, AND J.J. DE MIGUEL.

Bariloche, Rio Negro. Argentina

Conferencia; 13th International Conference on Solid Films and Surfaces; 2006

We have recently shown that the surface self-diffusion on metallic (111) faces is far from the purely stochastic, thermally activated, processes we are used to assume, for almost any temperature. While for high temperatures the atomic displacements  cover several near neighbor distances, at low temperatures recrossing jumps prevail. These jumps are double jumps ending on the original site, with no net displacement. In this work, continuing with our Molecular Dynamics simulations based on the embedded atom inter atomic potential, we study the detailed evolution of Cu dimers and trimers on a Cu(111) surface. We find that the geometrical constraints introduced by the inter atomic bonds, strongly modify the surface diffusion scheme.  While the diffusion of the island as a whole appears, as expected, strongly diminished for both island types, the mobility of the individual atoms within a dimer is largely enhanced.  Here again, we have found that the special triangular symmetry of the (111) face, when combined with the geometrical constraints introduced by the different island shapes, produces effects that go beyond the simple increase enhancement of the diffusion barriers.