INVESTIGADORES
ASCOLANI Hugo Del Lujan
artículos
Título:
The Structure of Atomic Sulfur Phases on Au(111)
Autor/es:
MIAO YU; H. ASCOLANI; G. ZAMPIERI; D. P. WOODRUFF; C. J. SATTERLEY; ROBERT G. JONES; V. R. DHANAK
Revista:
JOURNAL OF PHYSICAL CHEMISTRY
Editorial:
American Chemical Society
Referencias:
Año: 2007 vol. 111 p. 10904 - 10914
ISSN:
0022-3654
Resumen:
The
structural phases formed by atomic sulfur on Au(111) due to reaction with
molecular S2 have been investigated by
qualitative low-energy electron diffraction (LEED), scanning tunneling
microscopy, and normal incidence X-ray standing wavefield absorption (NIXSW)
combined with X-ray photoelectron spectroscopy (XPS). Three phases are
identified with increasing coverage, namely, a newly identified (5 _ 5) phase,
a (x3 _ x3)R30° phase,
and a complex phase. The (5 _ 5) phase, with a LEED pattern having the appearance
of a split-spot (x3 _ x3)R30° pattern, is interpreted in terms of local (x3
_ x3)R30° ordering within a (5 _ 5) ordered domain structure. The S atoms in
the (5 _ 5) phase occupy fcc hollow sites 1.56 Å above the outermost extended
Au(111) bulk atomic scatterer plane. A specific model of the ordering in this
phase is proposed that, together with the observed marginal stability of the
true, long-range-ordered, (x3 _ x3)R30° phase, indicates significant
short-range S-S repulsion and probably compressive surface stress. The complex
phase, that coexists in a poorly ordered state with the lower coverage atomic
chemisorption phases, is interpreted in terms of an incommensurate long-range
periodicity, but the NIXSW data shows clear evidence of local commensuration,
with the S atoms mainly close to atop sites relative to the underlying Au(111)
substrate; these data provide strong support for a previously proposed model
based on a sulfide layer of stoichiometry AuS.