M. Potthoff et al., STRUCTURE INVESTIGATIONS OF XE-ADSORBATE LAYERS BY SPIN-POLARIZED LOW-ENERGY-ELECTRON DIFFRACTION .1. (ROOT-3X-ROOT-3)R30-DEGREES-XE PT(111), Surface science, 322(1-3), 1995, pp. 193-206
The (root 3 x root 3)R30 degrees Xe layer on Pt(111) is studied by spi
n-polarized low-energy electron diffraction (SPLEED). In the experimen
t spin-polarized electrons from a GaAs photoemission source are scatte
red at the target, and the spin-dependent intensities are measured in
different diffracted beams. Corresponding calculations are performed u
sing a relativistic LEED program. Measurements and calculations show s
trong contributions from multiple scattering between the substrate and
the adlayer. The scattering contributions from the substrate are foun
d to dominate the general structure of asymmetry and intensity profile
s of integer order beams. In adsorbate-induced beams the contributions
from the substrate are significantly weaker but nevertheless clearly
present. The integer-order beams as well as the adsorbate-induced beam
s are suitable for structure investigations. Comparing measurements an
d calculations by means of r-factor analysis, we determine the local a
dsorption geometry. The Xe atoms are adsorbed in domains of fee and hc
p hollow sites on the Pt(111) surface with identical domain size proba
bility and random distribution of the domains. The distance between th
e adsorbate layer and the topmost substrate layer is found to be 4.2+/
-0.1 Angstrom. Measurements and calculations agree very well in genera
l.