A scanning tunnelling microscopy view of the surfactant-assisted growth ofiron on Cu(111)

We report a scanning tunnelling microscopy study of the growth of iron on C u(lll) using lead as a surfactant. In the absence of surfactant, the growth of iron on Cu(lll) proceeds in the form of three-dimensional islands, givi ng rise to an irregular granular film, with the presence of both face-centr ed cubic (fcc) and body-centred cubic crystallites whose relative populatio n depends on the film thickness. The deposition of iron is accompanied by a n active etching process, which results in chemical heterogeneity of the is lands and the appearance of vacancy islands in the substrate surface. On th e contrary, during the growth of iron on Pb/Cu(lll): (1) the reaction at th e interface is considerably limited, producing initially an almost perfect two-dimensional bilayer; (2) the subsequent growth results in a multilevel rough film due to limited interlayer mass transport; and (3) the iron film, continuous and monocrystalline, has the fee structure as suggested by the persistence of a (4 x 4) lead superstructure present on the top surface lay er up to at least six monolayers. (C) 2000 Elsevier Science B.V. All rights reserved.