Substituted Coronenes for Molecular Electronics: From Supramolecular Structures to Single Molecules
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Beschreibung
The ongoing miniaturization of silicon integrated circuits makes the understanding of
the electronic properties of nanoscale structures and the exploration of novel materials
and device concepts more and more important. One promising approach to construct
future electronic systems is the usage of organic molecules and utilizing their ability to
self-assemble and/or taking advantage of the possibility to achieve various electronic
functions just by modifying their chemical structures.
This thesis explores a highly conjugated molecular system, namely dodecakis(arylthio)-
coronenes (DATCs), with a view to potential applications as molecular electronic building
blocks. The techniques of scanning tunneling microscopy and spectroscopy are applied
to characterize the structural and the electronic properties of monolayers of these
molecules on metal surfaces.
Variations of the substituents allowed to specifically affect the self-assembly of the
molecules. Supramolecular structures with different orientations of the molecules relative
to the substrate and with different intermolecular interactions are obtained. The
growth of highly ordered supramolecular chains is observed in the case of the basic
molecular building block dodecakis(phenylthio)coronene (Cor-H) on Au(111) surfaces.
The formation of delocalized electronic states along the chains suggests the potential
of this system as a basis for novel organic materials with anisotropic charge transport
properties.
Substituents with varying electron-accepting or electron-donating ability are used to
modify Cor-H and enhance or prevent the molecular stacking. Assemblies of molecules
with molecular quantum dot behavior can also be obtained in this way. The tailored
functionalization allows a decoupling of the aromatic system of the molecules from
the substrate states, which in turn leads to the occurrence of single electron tunneling
effects. Different substitutions of the DATC system can thus be used to create desired
electronic functions.
Furthermore, several fabrication routs for nanoscale electrode structures were worked
out to “wire up” single molecules in a device-like configuration and to investigate their
electrical properties. In particular, the technique of electron-beam lithography in conjunction
with unconventional nanofabrication methods like electromigration were utilized
to fabricate nanometer-spaced metal electrodes. Such nanopatterns additionally
allowed to characterize the charge transport through embedded single molecules
Autor*in
Peter Kowalzik
Themen in »Substituted Coronenes for Molecular Electronics: From Supramolecular Structures to Single Molecules«
Resonant transport Scanning tunneling molecular devices