Based on a local study by means of scanning tunneling microscopy, we demonstrate that a small amount of Au grown on Si(1 1 1) either as Au-induced surface reconstruction or Au-rich islands, promotes dramatically the growth of Co silicide islands by solid phase reaction. We identified an outdiffusion of Si atoms from the substrate, induced by the Au-rich islands and limited to their vicinity, which results in a strong decrease of the formation temperature of the silicide islands. (C) 2012 Elsevier B. V. All rights reserved.