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@PHDTHESIS{Lennartz:14152,
      author       = {Lennartz, Maria Christina},
      title        = {{A}lternative systems for molecular electronics:
                      functionalized carboxylic acids on structured surfaces},
      volume       = {13},
      school       = {RWTH Aachen},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-14152},
      isbn         = {978-3-89336-667-5},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Information
                      / Information},
      pages        = {183 S.},
      year         = {2010},
      note         = {Record converted from JUWEL: 18.07.2013; RWTH Aachen,
                      Diss., 2010},
      abstract     = {Molecular electronics is recognized as a key candidate to
                      succeed the silicon based technology as soon as the end of
                      the semiconductor roadmap is reached. An important step
                      towards the realization of molecular electronics is the
                      combination of common CMOS devices and molecular elements to
                      new systems. Today, an advantageously used metal for wires
                      and interconnects in electronic industry is copper due to
                      its low resistance. Thus, it is essential to get a
                      fundamental understanding of organic/copper interfaces and
                      to combine functional molecular systems with linkers which
                      are copper sensitive. Within the scope of this work,
                      carboxylate molecules were investigated which chemically
                      bind to copper. They self-assemble in highly ordered
                      monolayer structures on, e.g., Cu(110) surfaces. Main task
                      of this work is the electronic characterization of the
                      combined molecule/metal system as well as the systematic
                      investigation of the influence of specific molecular parts
                      on the electronic transport. Scanning tunneling microscopy
                      (STM) was used as main technique to investigate the
                      topographic and electronic structures throughout the study,
                      but complementary techniques like XPS/AES, LEED and UV-VIS
                      spectroscopy were employed as well to get additional
                      information. The transport properties were investigated by
                      current-voltage (I-V) and current-distance (I-z)
                      spectroscopy. Distance-dependent I-V measurements enable the
                      detection of the density of states of the system with the
                      orbital energies appearing as peaks in the dI/dV curves.
                      Density functional theory based calculations (IFF-1, FZ
                      Jülich) were used to assign the measured peaks to specific
                      molecular orbitals. Thus, it is possible to display the
                      molecular orbitals with respect to their energies and their
                      spatial distribution. A detailed analysis of all
                      experimentally probed molecular orbitals has shown that the
                      calculated LDOS represents a characteristic fingerprint
                      corresponding to the substitution pattern of the
                      carboxylates bonded to Cu(110). It was shown that, e.g.,
                      nitrogen heteroatoms cause a shift in the molecular orbital
                      energies and lead to a system with smaller HOMO-LUMO gap.
                      With a detailed knowledge of the system parameters it is now
                      possible to make precise theoretical predictions on the
                      transport properties of other carboxylate species. Thus, a
                      first toolbox is composed which allows to combine molecular
                      moieties to build up a molecule linked to a metallic
                      electrode with a designed functionality. In a second step
                      carboxylates with a second functional group were
                      investigated. These molecules chemically bind to two
                      different electrode materials, e.g., with one side of the
                      molecule to copper and with the other side to gold. This
                      causes a diode functionality of the molecule within the
                      junction. The molecular self-assembly of these molecules
                      (here TMBA) was investigated on Au(111) surfaces. STM
                      investigations show ordered monolayer structures and XPS
                      measurements confirm a nondestructive chemisorption of the
                      molecules. The electron transport properties of the system
                      could be revealed from I-V measurements by monitoring the
                      local density of states as well as from I-z measurements by
                      calculating the molecule specific tunneling decay constant
                      $\beta$. Finally, a short excursion presents an alternative
                      approach to combine molecules with CMOS materials. This
                      approach does not use the metal layer as linking point but
                      the semiconductor areas. Semiconductor surfaces, like
                      Ge(001), with self-assembled metallic Pt nanowires build a
                      highly ordered 1D nanotemplate for the selective assembly of
                      triphenylphosphane molecules.},
      cin          = {IFF-6 / JARA-FIT},
      ddc          = {500},
      cid          = {I:(DE-Juel1)VDB786 / $I:(DE-82)080009_20140620$},
      pnm          = {Grundlagen für zukünftige Informationstechnologien},
      pid          = {G:(DE-Juel1)FUEK412},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/14152},
}