Metal-cluster growth with asymmetric diffusion and reversible aggregation on Si(111)7×7

The nucleation and growth behavior of metal nanoclusters on a Si(111)7×7 reconstructed surface is studied by using a kinetic Monte Carlo simulation. The main atomistic processes included in the model are diffusion of adatoms between half-unit cells of the 7×7 surface, and aggregation and decay of clusters occurred inside the half-unit cells. Considering the structural difference between faulted and unfaulted half-cells, the model introduces an asymmetric adatom aggregation mechanism by setting different effective binding energies of clusters in the two different types of half-cells, which gives rise to preferential occupation of clusters for the faulted half-cells. The simulation of the model produces growth mode transitions from hit and stick regime at low temperatures to self-organized growth regime at high temperatures. A comparison with relevant growth experiments demonstrates good qualitative agreement.