Local spectroscopy of bi-molecular self-assemblies
Fernández Torrente, Isabel

HaupttitelLocal spectroscopy of bi-molecular self-assemblies
Titelzusatzscreening, charge transfer, and magnetism at the molecular scale
TitelvarianteLokale Spektroskopie von bi-molekularen Systemen
Zusatz zur TitelvarianteAbschirmung, Ladungstransfer und Magnetismus auf der molekularen Skala
AutorFernández Torrente, Isabel
Geburtsort: Oviedo, Spanien
GutachterProf. Dr. José Ignacio Pascual
weitere GutachterProf. Dr. Martin Wolf
Freie SchlagwörterSTM, STS, molecular electronics, metal-organic interface, Kondo effect
DDC530 Physik
ZusammenfassungThe structural and electronic properties of molecular layers on
surfaces are driven by intermolecular and molecule-surface
interactions. This thesis contributes to decipher the role they play
in the formation of molecular complexes and explores on the
electronic and magnetic properties of the resulting nanostructures
with sub-molecular resolution.
By means of Low Temperature Scanning Tunneling Microscopy and
Spectroscopy (LT-STM and STS), we have investigated two examples of
bi-molecular organic ultra-thin films adsorbed on a Au(111) surface:
i) C60 and TPC, and ii) TTF and TCNQ. Density Functional Theory
(DFT) calculations of the molecular systems have been employed to
corroborate some of the experimental findings.
The individual growth of TPC molecules is extremely dependent on the
surface temperature. At a low threshold temperature of 80 K, TPC
self-organizes in stable molecular clusters that assemble in
multilayer islands driven by the TPC three dimensional shape, which
favors intermolecular pi-interactions. The mixing with C60
results in the formation of heteromolecular phases that exhibit
different patterns based on inclusion complexes mediated also by
pi-interactions. Local STS measurements reveal a strong
dependence of the C60 electronic properties on the molecular
neighborhood, detected as a shift of the molecular orbitals. By this
shift, we can resolve the polarizability of single molecules and
detect a small lifting of molecules from the metallic substrate.
The individual growth of TTF and TCNQ leads to two different
molecular networks. On the one hand, the adsorption of TTF is
mediated by a large charge donation into the surface, resulting in
the formation of a lattice of monomers based in long-range repulsive
interactions of electrostatic nature. On the other hand, TCNQ
interacts weakly with the underlying surface forming highly ordered
self-assembled domains. Co-deposition of TTF and TCNQ on Au(111)
form highly anisotropic mixed domains where TTF and TCNQ are
distributed in a periodic row arrangement and couple differently to
the surface. The periodicity of the TTF-TCNQ layer generates a
potential on the surface across the molecular rows that creates at
the interface two hybrid bands with different dimensionality. These
bands are spatially localized under the molecular rows. STS unveils
a metal-like dispersion along one dimension underneath the TCNQ
rows. Further STS measurements reveal also a characteristic
spin-Kondo fingerprint in the TCNQ molecules. TTF donates one
electron to the TCNQ in the self-assembled structure resulting in
single molecule magnetism of pi-character. Intra-molecular
resolution of the spin-Kondo fingerprint reveals the coupling of the
spin with vibrations induced in the molecule, dependent on lateral
position inside the TCNQ.
Dataobject from FUDISS_thesis_000000004806
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Seitenzahl110, II S.
Fachbereich/EinrichtungFB Physik
Rechte Nutzungsbedingungen
Tag der Disputation09.07.2008
Erstellt am13.08.2008 - 12:31:11
Letzte Änderung19.02.2010 - 12:11:05
Statische URLhttp://www.diss.fu-berlin.de/diss/receive/FUDISS_thesis_000000004806