Ag/Cu(111) surface structure and metal epitaxy by impact-collision ion-scattering spectroscopy and scanning tunneling microscopy - art. no. 035402

We have investigated the growth of 3 monolayers (ML) of Ag on Cu(111) for s ubstrate temperatures from 170 through 640 K by using time of flight-impact collision ion scattering spectroscopy (TOF-ICISS). Also, scanning tunnelin g microscopy (STM) topographs were taken after the deposition of 0.8 ML of Ag atoms at room temperature (RT). We observed that for deposition of Ag at substrate temperatures above 300 K, two different types of epitaxial growt h exist: Ag[11 (2) over bar]parallel to Cu[11 (2) over bar] (type-n) and Ag [(11) over bar2]parallel to Cu[11 (2) over bar] (type-r). The growth modes of the Ag thin films on Cu(111) surfaces depend strongly on the temperature during deposition with the Ag(111) planes having a preferred orientation o f either type-n growth mode or type-r growth mode as a function of the Cu s ubstrate temperature. A part of the first-layer Cu atoms (20% of the surfac e) is displaced at low Ag coverage, where the stacking changes abruptly fro m fcc to hcp sites because of the Ag atom deposition at 603 K. The STM imag e of the Ag coverage of 0.8 ML showed a periodic array of triangular misfit dislocation loops at the deposition temperature of RT. The triangular shap e in a localized region where the stacking {Ag-Cu (A)-Cu (B)-Cu (C)} is rep laced by {Ag-Cu (C)-Cu (B)-Cu (C)} in the first substrate plane. At 603 K, surface alloying of the Ag-Cu. system was confirmed for Ag coverage below 0 .15 ML. The experimental results concerning Ag/Cu(111) show many similariti es to those in the previous study of Au/Ni(111). This would suggest that ob served oscillations in the growth mode, dependent on the substrate temperat ure during deposition, may be a general phenomenon on solid surfaces, in ca ses of large misfit since it has now been seen for both Au/Ni(111) and Ag/C u(111) systems. Furthermore, Cu atoms deposited on the Ag/Cu(111) system fo rm islands with the same orientation of Ag(111) planes. The Cu atoms underg o surface diffusion at room temperature in the direction of type-n . domain s for both type-r and type-n modes Ag substrates.