Combined photoelectron and X-ray diffraction from ultrathin Fe films on Cu Au 001/

X-ray specular reflectivity, in-plane grazing incidence X-ray diffraction GIXRD.and photoelectron diffraction PED. have been employed to study the FerCu3Au 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. PED 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 fcc substrate; the bulk-like Fe bcc structure has been observed for an 18-A° 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 fcc sites. A consistent fraction of a monolayer of Au is still present on top of the 18-A° Fe bcc film. q2000 Elsevier Science B.V. All rights reserved.