Early stages of formation of the Ag-Ni(111) interface studied by grazing incidence x-ray diffraction and x-ray photoelectron diffraction

摘要

Ultra-thin Ag/Ni(111) reconstructed interfaces have been revisited by a combination of in-situ grazing incidence x-ray diffraction (GIXD) and x-ray photoelectron diffraction (XPD) in order to determine the growth mode and to evaluate the interface spacing. Evidence for predominance of single-layer growth in the early stages was obtained through the analysis of the x-ray diffraction rods from the Ag/Ni(111) (52~(1/2) ×52~(1/2))R13.9° reconstructed interface, whereas photoelectron diffraction patterns could reveal traces of second-layer Ag scatterers before full wetting of the substrate. Refinement of the atomic coordinates provided by quenched molecular dynamics simulation on the basis of the new x-ray data set enabled us to assess the Ag/Ni average interplanar distance, which was found unexpanded at 2.44 ± 0.07 A, in contrast with recent determination by low-energy electron diffraction and microscopy. For increasing deposited amounts, both GIXD and XPD showed the expected features of two- and three-layer silver epitaxial overgrowths.