Simulation study of asymmetric aggregation behavior of adatoms on Si(1 1 1)7×7

We perform detailed simulations of the nucleation and growth of adatoms on the Si(1 1 1)7×7 reconstructed surface based on a modified cooperative diffusion model, and analyze the effect of different asymmetric diffusion and aggregation mechanisms on the growth behavior. We demonstrate that the asymmetry controlled by the difference of effective binding energies between faulted and unfaulted half cells has a strong influence on the preference of occupation of faulted half cells at higher temperatures for both irreversible and partially reversible aggregation. Using the occupation preference as a measure of cluster ordering, the simulation clearly shows growth mode transition from random nucleation at low temperatures to ordered self-organized growth at high temperatures in the case of partially reversible aggregation.