Combined photoelectron and X-ray diffraction from ultrathin Fe films on Cu3Au(001)

X-ray specular reflectivity, in-plane grazing incidence X-ray diffraction (GIXRD) and photoelectron diffraction (PED) have been employed to study the Fe/Cu3Au(001) system at the ALOISA beamline (Trieste Synchrotron, Italy). In-plane GIXRD has been used to determine the epitaxial strain of the film lattice by (H00) radial scans around the Cu3Au(200) diffraction peak. FED has been employed in forward scattering conditions to determine the vertical spacing of the topmost layers and to look at atomic exchange processes. At very low coverage, Fe grows pseudomorphically on the fee substrate; the bulk-like Fe bcc structure has been observed for an 18-Angstrom thick Fe film. The PED analysis suggests that, at 1 ML Fe coverage, a full Au layer is segregated onto the surface with the Au atoms sitting in their fee sites. A consistent fraction of a monolayer of Au is still present on top of the 18-Angstrom Fe bcc film.