X-RAY PHOTOELECTRON AND AUGER-ELECTRON FORWARD-SCATTERING STUDIES OF LATTICE EXPANSIONS AND CONTRACTIONS IN EPITAXIAL-FILMS

X-ray photoelectrons and Auger electrons emitted by atoms in a lattice undergo forward scattering by neighboring atoms during their propagation through the lattice. This forward scattering produces enhancements in the emission intensity along nearest-neighbor directions. In the present work, the directions of these enhancements are used to infer lattice expansions and contractions in epitaxial films. Epitaxial films of Mn grown on Cu(100) expand outwards and on Ag(100) contract inwards, as compared to a simple extension of the face-centered-cubic substrate lattice. Thus, in both cases, the Mn lattice is body-centered-tetragonal. This expansion and contraction is reasonable since the Mn atom is intermediate in atomic volume between Cu and Ag, so that it must by compressed laterally to match the Cu(100) surface and stretched laterally to match the Ag(100) surface. However, it is of interest that the combined magnitude of these effects yield, in both cases, Mn with a larger atomic volume than that found in elemental α-Mn. Nevertheless, epitaxial Mn sandwich structures consisting of 60-ML-Cu/3-ML-Mn/ Cu(100) and 60-ML-Ag/3-ML-Mn/Ag(100) were found not to be ferromagnetic even at 77 K. Experiments on the annealing of monolayer-range Mn films demonstrate that neither Cu(100) nor Ag(100) is wet by Mn. Studies of epitaxial Fe and Cu films on Ag(100) demonstrate that in both cases a vertical contraction occurs that yields a lattice quite close to body-centered-cubic. © 1990, American Vacuum Society. All rights reserved.