The role of an ultra-thin Cu layer in the nucleation and growth of Fe/Si nanostructures on Si(111) was investigated using scanning tunnelling microscopy. For deposition onto the bare Si(111)-(7 x 7) surface, the diffusion and nucleation of Fe atoms were significantly influenced by reaction with the Si substrate. But for the Si(111)-(5 x 5)–Cu surface it caused a decoupling of the diffusion and nucleation on, and reaction with, the surface. At ≤350C, this decoupling resulted in a diffusion behaviour which could be described by conventional nucleation theory, using a single value (49eV) for the effective diffusion barrier, and a critical nucleus size of 2. It was shown that Fe atoms alone contributed to the critical nucleus.

Diffusion, Nucleation and Reaction in a Three-Component System: Fe on Si(111)-'5x5'–Cu. K.Paredis, D.Smeets, A.Vantomme: New Journal of Physics, 2009, 11[9], 093019