Structure of ultrathin iron films on a highly asymmetrical substrate: [formula omitted

Abstract

The morphology of epitaxial Fe films on Cu(311) is examined in situ by spot profile analyzing-low-energy electron diffraction (SPALEED). The Cu(311) substrate is characterized by a trough-like surface structure with uniaxially arranged close-packed atom rows. Deposition at 140 K leads to 3D growth of bcc Fe(211). Likewise, this overlayer orientation is highly asymmetrical: close-packed Fe atom rows are aligned parallel to those of the Cu substrate. Substrate-induced uniaxial stress causes a periodic faceting of the growth front along the row direction. Completion of coalescence takes place at 5 ML and leads to the occurrence of two structurally different fractions of the overlayer: the film is pinned to a lattice arrangement which is dictated by the substrate and is likely to correspond to a fcc-like structure. The periodic faceting of the film surface, on the other hand, enables partial relaxation toward strained bcc structure to persist in the top layers of the film.