A low energy ion scattering investigation of the structure of bilayer islands of nanometric size in the initial stages of growth of iron on Cu3Au (001)

We report on the initial stages of growth of Fe on a well-defined Cu3Au(001 ) substrate as a function of the temperature of deposition in the range 150 -350 K. The structure and morphology of the deposit have been studied by lo w energy ion scattering (LEIS) under the so-called impact collision conditi ons (ICISS). Comparison of ion scattering results with simulations in two d imensions of the particle trajectories allowed us to obtain information on the structure and morphology of Fe islands. Ion scattering results have bee n analysed in combination with He diffraction data obtained in the same app aratus, under the same experimental conditions. Both ICISS and He scatterin g indicate that growth initially proceeds through nucleation of many small islands. The two techniques provide independent and fully compatible estima tes of the average separation between islands that at one layer equivalent increases from similar to 30 Angstrom at 165 K to similar to 60 Angstrom at 350 K. ICISS data are fully consistent with the model of initial growth of two-layer thick islands proposed in a recent He scattering investigation [ Phys. Rev. B 62(2000) 13121]. The bilayer growth mode is effective at tempe ratures up to 350 K, even if at this temperature Fe intermixing with substr ate atoms cannot be ruled out. Bilayer islands grow pseudomorphically with a relevant tetragonal strain, (C) 2001 Elsevier Science B.V. All rights res erved.