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@BOOK{Go:136360,
author = {Goß, Karin},
title = {{I}nteractions between parallel carbon nanotube quantum
dots},
volume = {30},
school = {Universität Duisburg},
type = {Dr.},
address = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-136360},
isbn = {978-3-89336-740-5},
series = {Schriften des Forschungszentrums Jülich. Reihe
Schlüsseltechnologien / key technologies},
pages = {VIII, 139 S.},
year = {2011},
note = {Record converted from JUWEL: 18.07.2013; Universität
Duisburg, Diss., 2011},
abstract = {The subject of this thesis is molecular interactions which
are investigated using the example of parallel quantum dots
formed in the individual strands of a carbon nanotube rope.
For molecular electronics, carbon nanotubes offer a variety
of macromolecular structures and by combining several
nanotubes into a rope, also a generic system to probe
molecular interactions. First, the structure of the
contacted rope is characterized by tip-enhanced Raman
spectroscopy (TERS). We observe a clear resonance effect for
the Raman scattering process, which is up to now not
considered in the literature on TERS of carbon nanotubes. By
extracting the diameter, metallicity and chirality, seven
carbon nanotubes within the rope are identified. A redshift
of their optical transition energies is attributed to
interactions between the strands. In quantum transport
measurements, the nanotubes are found to form interacting
parallel quantum dots. Within the framework of master
equations, a model is developed to describe the transport
via the quantum dot system, where the parallel dots are
capacitively and tunnel coupled. Employing this model, seven
parallel quantum dots are characterized by their
interactions. Along with changing interface properties
predicted by the TERS characterization, the coupling to the
two contacts is very asymmetric for most of the quantum
dots. Additionally, the coupling to the gate electrode is
found to vary strongly for individual dots, allowing one to
tune the quantum dot system into different configurations
and selectively add electrons to individual strands of the
rope. Exploiting this differential gating effect, the
magnitude of the molecular interactions can be investigated.
Here, we find that individual strands within one carbon
nanotube rope can interact very distinctly. Amongst the
coupled quantum dots with a coupling stronger than
previously assumed, we also find only capacitively
interacting or completely uncoupled quantum dots within the
one device. The tunnel coupling is a hybridization of
quantum dot states which, in principle, are comprised of the
molecular orbitals. In particular, the sign of the
hybridization amplitude contains information about the
involved wavefunctions, where we always find a negative
amplitude denoting the overlap of wavefunctions with the
same sign. The hybridization can be manipulated by an
applied magnetic field and hence selectively suppressed due
to spin effects. Here, the differential gating allows for
tuning to distinct spin configurations of the quantum dot
system. In conclusion, we demonstrate a tunable quantum
device which provides the possibility of probing molecular
interactions by quantum transport spectroscopy. The
additional characterization using TERS represents a novel
combination of two experimental techniques with great
potential in the field of molecular electronics.},
cin = {PGI-6},
ddc = {500},
cid = {I:(DE-Juel1)PGI-6-20110106},
typ = {PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/136360},
}