Full-hemispherical photoelectron-diffraction data from Cu(001): Energy dependence and comparison with single-scattering-cluster simulations

Abstract

Angular distributions of several photoelectron and Auger transitions have been measured above a Cu(001) single crystal at 16 different kinetic energies between 60 and 1740 eV. The results are presented as 2m full-solid-angle intensity maps -diffractograms -that permit a clear representation of the relative importance of various scattering processes at each energy and the evolution of intensity patterns with energy. The experiments are compared with single-scattering-cluster (SSC) simulations performed at corresponding energies. This serves to probe the accuracy of the SSC formalism over a vast energy and angular range and to illustrate the role of the angular momentum of the final state, polarization effects, and temperature effects. Rather good agreement is found for positions of angular patterns down to very low energies, with problems mainly in relative intensities. The sensitivity of low-energy diffraction patterns to bond lengths is demonstrated.

X-ray photoelectron diffraction study of Cu(111): Multiple scattering investigation

“…Again, this experimental V-like feature is better reproduced by the MSC code. Interferences of two neighbouring h1 1 0i directions generate modulations along the 1 1 1 planes with maxima near [1 2 1] (E) [6]. Similar features (F) appear in the ½2 1 1 direction along the same planes, produced by interferences of the scattering by [1 1 0] and invisible ½1 0 1 neighbours.…”

“…It has a V-like shape with a small asymmetry visible in the measured and SSC interference patterns, originating from photon polarization effects owing to the oblique photon incidence in our setup. These asymmetry effects are especially visible at lower energies [6]. Presently, our special setup geometry and therefore this asymmetry behaviour cannot be simulated with EDAC.…”

“…The X-ray tube contains a MgKa (hm = 1253.6 eV) and SiKa (hm = 1740 eV) twin anode. The samples are fixed on a computer-controlled two-axis goniometer capable of scanning the emission angle over the full hemisphere above the surface [5][6][7][8][9][10]. Data has been collected for a polar angel range h 2 [0°, 78°] and an azimuthal angle range / 2 [0°, 360°].…”

Electronic structure and Fermi surface of two-dimensional rare-earth silicides epitaxially grown on Si(111)

“…Rotation is computer controlled for motorized angle-scanned data acquisition. 19,20 SiK ␣ was used for x-ray photoelectron spectroscopy in order to check the cleanness of the sample. Monochromatized He I and He II radiations ͑21.2 and 40.8 eV, respectively͒ from a discharge lamp were used for ultraviolet spectroscopy.…”

Direct evidence for ferroelectric polar distortion in ultrathin lead titanate perovskite films

“…The XPD measurement system comprises a hemispherical electron energy analyzer with a three-channel detector, an x-ray photon source with two possible energies (hν = 1253.6 eV and 1740 eV for MgKα and SiKα radiation, respectively), and a computer-controlled two-axis goniometer capable of rotating the photoelectron emission angle over the full hemisphere above the surface [26,27].…”