Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 4: Epitaxie und Wachstum I

O 4.2: Vortrag

Freitag, 4. März 2005, 11:00–11:15, TU EB202

Strain relaxation in ultrathin Ni films grown on Ir(100)-(1x1) and Ir(100)-(5x1)-H — •Andreas Klein, Bernd Gumler, Lutz Hammer, and Klaus Heinz — Lehrstuhl für Festkörperphysik , Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen

We report on the growth of Ni films both on the metastable (1x1) phase and on the hydrogen-induced (5x1)-H phase of the Ir(100) surface in the coverage regime 4-10 monolayers (ML) applying STM and LEED. Whilst the (1x1) phase corresponds to the bulk-like truncated crystal, the (5x1)-H phase consists of long Ir wires of single atomic width which reside on this (1x1) phase in (on average) 5-fold lateral periodicity. On both templates an almost perfect layer-by-layer growth in the low coverage regime is followed by strain-relief controlled growth above 4 ML coverage. In this regime islands of 5 atoms width grow only one-dimensionally and eventually form irregular grids on the surface. Only with the completion of a layer the spaces within the grids are filled so that flat and homogeneous, but strained layers are formed. With film thicknesses in the range 6-8 ML the layerwise growth becomes less perfect and, at about 10 ML, dislocations are formed. For the (1x1) substrate the structures mentioned extend in both the [011] and [01-1] directions, whereas on the (5x1)-H phase the Ir wires at the film-substrate interface impose their unidirectionality on the higher coverage films. Only above a coverage of about 10 ML this differences between the two phases disappear and the nickel films exhibit similar patterns of strain relief.