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@PHDTHESIS{He:807740,
      author       = {Heß, Volkmar},
      title        = {{S}canning tunneling microscopy of single-molecule magnets
                      and hybrid-molecular magnets: {T}wo approaches to molecular
                      spintronics},
      volume       = {121},
      school       = {Universität Köln},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-02158},
      isbn         = {978-3-95806-128-6},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {X, 127 S.},
      year         = {2016},
      note         = {Universität Köln, Diss., 2016},
      abstract     = {Molecular spintronics attempts both to improve the
                      properties of current electronic devices and develop
                      completely new devices by combining the advantages of
                      molecular electronics and spintronics into one research
                      field. Investigating and evaluating the properties of
                      molecular magnets and to eventually employ them in devices
                      is a major goal of molecular spintronics. Two different
                      kinds of molecular magnets are promising candidates for
                      device development: Single-molecule magnets (SMMs) and
                      hybrid-molecular magnets. Both are ideal building blocks for
                      spintronic devices, such as spin-transistors and
                      spin-valves. However the fabrication of devices requires the
                      deposition on surfaces. Due to the interaction between
                      molecules and surfaces being highly complex, only a
                      fundamental understanding of these phenomena will eventually
                      lead to the succesful application of molecular magnets in
                      devices. To improve the understanding of the
                      molecule-surface interaction both approaches have been
                      investigated experimentally in this dissertation. Since
                      surfaces are prone to contamination, these experiments were
                      conducted in ultra-high vacuum. To gain more insight in such
                      systems and to understand the adsorption phenomena, their
                      structural, electronic and magnetic properties were studied
                      on a microscopic scale with scanning tunneling microscopy
                      (STM) and spectroscopy (STS). The interaction between SMMs
                      and surfaces was exemplarily studied by depositing
                      {Ni$_{4}$} on Au(111). {Ni$_{4}$} is a recently synthesized
                      SMM where a cubane {Ni$^{II}_{4}$($\mu_{3}$ - Cl)$_{4}$}
                      core is responsible for the magnetic properties [1]. The
                      magnetic core is protected by organic ligands exhibiting a
                      thioether surface functionalization. Since thioether
                      functionalized ligands had been widely neglected in earlier
                      experiments, the deposition of {Ni$_{4}$} on Au(111) from
                      solution and the resulting adsorption phenomena were studied
                      by XPS and STM. Both methods revealed strong evidence for a
                      ligand detachment during adsorption. The magnetic core
                      however might be still structurally intact as indicated by
                      XPS. Attempts to desorb the detached ligands and to
                      subsequently image the magnetic core with STM by
                      $\textit{in-situ}$ post-annealing were unsuccessful. Instead
                      the post-annealing lead to the decomposition of the magnetic
                      core and to a most likely sulfur induced reconstruction of
                      the Au(111) surface. As a results of this study new
                      strategies have been proposed to avoid the ligand detachment
                      in future experiments. In a complementary approach the
                      interaction between molecules and surfaces is exploited for
                      the formation of hybrid-molecular magnets. Here,
                      comparatively stable non-magnetic molecules are deposited on
                      magnetic surfaces. The interaction leads to a magnetic
                      molecule-surface hybrid, or "hybrid-molecular magnet". This
                      approach requires a magnetic substrate. For this task the
                      well known Fe/W(110)system was chosen and charaterized by
                      spin-polarized STM (SP-STM). The fabrication of suitable
                      magnetic tips for SP-STM is a well known challenge due to
                      its poor predictability and reproducibilty. The
                      characterization of tips was performed by SP-STM
                      measurements on the Fe/W(110) system and reveals that
                      Cr-coated tips exhibit the required out-of-plane
                      magnetization direction for the following experiments on
                      hybrid-molecular magnet systems. Furthermore an effective
                      spin polarization of up to 12.4\% for the whole tip-sample
                      tunnel junction was found. [...]},
      cin          = {PGI-6},
      cid          = {I:(DE-Juel1)PGI-6-20110106},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/807740},
}