Fe deposition on Pt(111): a route to Fe-containing Pt-Fe alloy surfaces

Bimetallic surfaces formed by the evaporation of Fe onto a Pt(l 11) single crystal at 350 K in ultrahigh vacuum were examined by X-ray electron spectroscopy, low energy electron diffraction (LEED), and low energy ion scattering. Some alloying occurs upon deposition, but heating thick Fe films to 600-850 K causes diffusion of Fe into the near-surface region and forms an alloy layer at the surface which contains 0.5-ML Fe. Annealing to 750 K orders the alloy and results in formation of a diffuse 2 x 2 LEED pattern. This procedure produces Fe-containing alloy surfaces that are more thermally stable against Pt surface segregation than expected from the behavior of Pt80Fe20(l 11) bulk crystals, and significant amounts of Fe are stabilized in the surface layer until temperatures as high as 950 K. Alloying with Fe causes a +0.40-eV chemical shift in the Pt(4f(7/2)) peak, but no chemical shift of the Fe(3d(5/2)) peak in the bulk of the crystal. (C) 2002 Elsevier Science B.V. All rights reserved.