Al-rich Fe_0.85Al_0.15(1 0 0), (1 1 0) and (1 1 1) surface structures

Based on previous photoemission findings, the influence of newly observed aluminum surface segregation at the low (1 1 0), (1 0 0) and (1 1 1) index surfaces of the A₂ body-centered Fe_0.85Al_0.15 random alloy is explored. Scanning Tunneling Microscopy, Low-Energy Electron Diffraction and Grazing-Incidence X-ray Diffraction are combined to explore surface structures and topographies. The formation of a surface composition close to the B₂ Fe_0.5Al_0.5 occurs with the appearance of (i) a long-range pseudo-hexagonal incommensurate superstructure with a periodicity of ~18 Å on the (1 1 0) surface, (ii) a (1×1) termination on the (1 0 0) surface and (iii) a intense vicinal faceting of the (1 1 1) surface in the form of triangular pits.