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@PHDTHESIS{Mercurio:50820,
author = {Mercurio, Giuseppe},
othercontributors = {Tautz, Frank Stefan},
title = {{S}tudy of molecule metal interfaces by means of the normal
incidence x-ray standing wave technique},
volume = {49},
address = {Aachen},
publisher = {Forschungszentrum Jülich, Zentralbibliothek [u.a.]},
reportid = {RWTH-CONV-113345},
isbn = {978-3-89336-816-7},
series = {Schriften des Forschungszentrums Jülich : Reihe
Schlüsseltechnologien},
pages = {XXII, 361 : Ill., graph. Darst.},
year = {2012},
note = {Ausgezeichnet mit dem Jülicher Exzellenz-Preis für
Nachwuchswissenschaftler/innen 2013.; Zugl.: Aachen, Techn.
Hochsch., Diss., 2012},
abstract = {Functional surfaces based on monolayers of organic
molecules are currently subject of an intense research
effort due to their applications in molecular electronics,
sensing and catalysis. Because of the strong dependence of
organic based devices on the local properties of the
molecule-metal interface, a direct investigation of the
interface chemistry is of paramount importance. In this
context, the bonding distance, measured by means of the
normal incidence x-ray standing wave technique (NIXSW),
provides a direct access to the molecule-metal interactions.
At the same time, NIXSW adsorption heights are used to
benchmark different density functional theory (DFT) schemes
and determine the ones with predictive power for similar
systems. This work investigates the geometric and chemical
properties of different molecule/metal interfaces, relevant
to molecular electronics and functional surfaces
applications, primarily by means of the NIXSW technique. All
NIXSW data are analyzed with the newly developed open source
program Torricelli, which is thoroughly documented in the
thesis. In order to elucidate the role played by the
substrate within molecule/metal interfaces, the prototype
organic molecule
3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) is
explored on the Ag(110) surface. The molecule results more
distorted and at smaller bonding distances on the more
reactive Ag(110) surface, in comparison with the Ag(100),
the Ag(111) and Au(111) substrates. This conclusion follows
from the detailed molecular adsorption geometry obtained
from the differential analysis of nonequivalent carbon and
oxygen species (including a careful error analysis).
Subsequently, the chemisorptive PTCDA/Ag(110) interaction is
tuned by the co-deposition of an external alkali metal,
namely K. As a consequence, the functional groups of PTCDA
unbind from the surface, which, in turn, undergoes major
reconstruction. In fact, the resulting nanopatterned surface
consists of alternated up and down reconstructed Ag terraces
covered by PTCDA molecules partly unbound with respect to
the pure molecular phase. This picture follows from a
combination of NIXSW, XPS, UPS, LEED and STM experiments.
Within the context of the functional surfaces, the
interaction of the molecular switches azobenzene (AB) and
3,3',5,5'-tetra-tert-butyl azobenzene (TBA) adsorbed on the
Ag(111) surface is investigated. The bonding distance of
TBA, only slightly greater compared to AB, indicates that
the desired geometric decoupling of the photochromic moiety
to enable the trans to cis switching in the adsorbate state
does not occur. In particular, the measured adsorption
heights of nitrogen, in excellent agreement with the
dispersion corrected DFT-PBE calculations, suggest that both
molecules are in the trans isomerization. Moreover, an
detailed adsorption geometry of AB and TBA, including the
carbon atoms, is obtained by means of the Fourier vector
analysis in the Argand diagram. This method allows the
multiple molecular degrees of freedom of large and flexible
molecules to be explored and provides structural parameters,
e.g., the phenyl ring tilt angle and torsion angle, with
unprecedented accuracy. Other functional surfaces that are
appealing for molecular electronics applications are the 2D
metal-organic networks. In this work, the self-assembled
monolayer of the prototypical molecular ligand terephthalic
acid (TPA) on the Cu(100) surface, prior to additional metal
deposition, is examined. NIXSW data reveal a significantly
distorted molecule with the carboxylate groups covalently
bound to the Cu atoms underneath and the carbon backbone
arc-like bent. This evidence suggests an intermolecular
interaction mediated by the substrate, as also supported by
previous HREELS measurements. Finally, the disagreement
between the experimental adsorption geometry and the DFT-PBE
prediction motivates further theoretical studies to improve
the understanding of this prototypical molecule-metal
interface.},
keywords = {Adsorbat (SWD) / A-15-Struktur (SWD) / Röntgenstrahlung
(SWD)},
cin = {134110 / 130000},
ddc = {530},
cid = {$I:(DE-82)134110_20140620$ / $I:(DE-82)130000_20140620$},
shelfmark = {61.05.jh * 68.37.Ef * 68.49.Uv * 68.43.Fg * 82.80.Pv},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
urn = {urn:nbn:de:hbz:82-opus-42905},
url = {https://publications.rwth-aachen.de/record/50820},
}
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