Diffusion, nucleation and reaction in a three-component system: Fe on Si(111)-'5 x 5'-Cu

The role of an ultrathin Cu layer on the nucleation and growth of Fe/Si nanostructures on Si(111) is investigated using scanning tunneling microscopy. While for deposition on the bare Si(111)-7 x 7 surface, the diffusion and nucleation of Fe atoms are significantly influenced by the reaction with the Si substrate, the Si(111)-'5 x 5'-Cu surface causes a decoupling of the diffusion and nucleation on and reaction with the surface. For moderate temperatures (T <= 350 degrees C), this decoupling results in a diffusion behaviour, which can be adequately described by the conventional nucleation theory (CNT), using a single value for the effective diffusion barrier E* = 0.49 eV and a critical nucleus size i = 2. Furthermore, it is evidenced that only Fe atoms contribute to the critical nucleus and E* thus describes the diffusion and nucleation of Fe atoms. On the other hand, at temperatures above 400 degrees C, the island growth kinetics change considerably, i. e. the preferential step edge nucleation and three-dimensional growth are observed, and CNT is no longer applicable.

Publication year:2009

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BOF-publication weight:3

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Authors from:Higher Education