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@ARTICLE{Bauer:826068,
author = {Bauer, O. and Schmitz, C. H. and Ikonomov, J. and
Willenbockel, M. and Soubatch, S. and Tautz, F. S. and
Sokolowski, M.},
title = {{A}u enrichment and vertical relaxation of the {C}u$_{3}$
{A}u ( 111 ) surface studied by normal-incidence x-ray
standing waves},
journal = {Physical review / B},
volume = {93},
number = {23},
issn = {2469-9950},
address = {Woodbury, NY},
publisher = {Inst.},
reportid = {FZJ-2017-00328},
pages = {235429},
year = {2016},
abstract = {We have investigated the Cu3Au(111) surface, prepared under
ultrahigh vacuum conditions by sputtering and annealing, by
low energy electron diffraction (LEED), scanning tunneling
microscopy (STM), x-ray photoelectron spectroscopy, and
normal incidence x-ray standing waves (NIXSW). We find the
surface to be depleted with Cu and enriched with Au at the
same time, yielding a nominal Cu:Au ratio of 0.61:0.39 in
the topmost layer. The STM images reveal that the first
layer is nearly closely filled with atoms and contains a
small amount of vacancies with an area concentration of
about $5\%.$ Together with the Au enrichment, these cause
local short-range disorder of the Au p(2×2) reconstruction.
From this data, the average stoichiometry of the p(2×2)
surface unit cell is estimated at Cu2.22Au1.44□0.20
(instead of Cu3.00Au1.00□0.00 of the ideal surface; □
denotes an atomic vacancy site). From NIXSW we find a
significant outward relaxation of both the Cu and Au atoms
of the topmost layer by 0.28 Å and 0.33 Å, which
corresponds to $13\%$ and $15\%$ of the (111) bulk layer
spacing of Cu3Au. We suggest that this originates from a
widening of the first/second layer spacing, by $6.8\%$ and
$8.8\%$ for the Cu and Au atoms, respectively, plus an
additional rigid increase in the second/third layer spacing
by $6.2\%.$ We explain this by steric repulsions between Au
atoms of the topmost layer, replacing smaller Cu atoms, and
Au atoms in the second layer in combination with disorder.
Finally, a lateral reconstruction, similar to that on the
Au(111) surface, but with a much larger periodicity of 290
Å, is identified from LEED.},
cin = {PGI-3},
ddc = {530},
cid = {I:(DE-Juel1)PGI-3-20110106},
pnm = {142 - Controlling Spin-Based Phenomena (POF3-142)},
pid = {G:(DE-HGF)POF3-142},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000378050600006},
doi = {10.1103/PhysRevB.93.235429},
url = {https://juser.fz-juelich.de/record/826068},
}