X-ray photoelectron holography of ultrathin film and single crystal Cu(111): improving the accuracy of bond-length determination

Forward-scattering diffraction patterns from single-crystal Cu(111) substrates and an epitaxial film of FCC Cu/Ir(111) have been analyzed to produce real-space images of the atomic lattice by Fourier-transform holography. The accuracy of atomic positions is found to be better in the single-crystal holograms than in the ultrathin film of copper. The angular dependence of the atomic scattering factor produces a shift in the position of atoms in the holographic image, and causes the atom image to be asymmetric. Model calculations reproduce the atom shift and asymmetry. A modified Fourier-transform algorithm is shown to correct for both the atom-shift and the image asymmetry.