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@PHDTHESIS{Flatten:875393,
      author       = {Flatten, Tim},
      title        = {{D}irect measurement of anisotropic resistivity in thin
                      films using a 4-probe {STM}},
      volume       = {213},
      school       = {Universität Köln},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2020-02002},
      isbn         = {978-3-95806-460-7},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {VIII, 129 S.},
      year         = {2020},
      note         = {Universität Köln, 2019},
      abstract     = {Four-point electronic transport measurements have proven to
                      be the best choice for determining the resistance of a
                      sample and thus the resistivity properties, because the
                      contact resistances are negligibly small. Various techniques
                      using the 4-point method have been explored, whereby the
                      4-probe scanning tunneling microscope is a powerful
                      experimental tool to measure the sample resistance on small
                      length scales including the possibility to vary probe
                      spacings. Nowadays, layered materials are in the focus of
                      interest due to their intriguing fundamental properties and
                      their high potential in a variety of applications. In
                      addition, they are also possible parenting materials for
                      so-called 2D materials due to a typically weaker chemical
                      bonding along one crystalline axis. Beside the famous
                      parent-materials such as graphite, hexagonal boron nitride,
                      and transition metal dichalcogenides, there is a further
                      class of layered materials, namely the so-called MAX phases
                      comprising both metal as well as ceramic properties. This
                      unique combination stems from a complex, anisotropic bonding
                      scheme that leads to an anisotropic conductivity. Growing
                      those layered materials as thin-film samples, they comprise
                      usually a bonding anisotropy perpendicular to the surface.
                      Thus, an anisotropy between the in-plane and out-of-plane
                      conductivities is expected. Such anisotropic electronic
                      transport properties are characterized by introducing the
                      resistivity as a second rank tensor. The resistivity is then
                      expressed by a symmetry-dependent number of independent
                      components that can be determined from resistance
                      measurements along different directions of the sample. The
                      in-plane resistivity components can be easily characterized
                      using several well-known methods, while up to now the
                      out-of-plane resistivity cannot be determined without any
                      additional sample treatment or modication, if a material can
                      only be prepared in thin-film form. Therefore, a novel
                      direct and parameter-free method is developed in this thesis
                      for the accurate determination of the out-of-plane
                      resistivity without any further treatment of the sample. A
                      multi-probe scanning tunneling microscope is used to carry
                      out 4-probe transport measurements with variable probe
                      spacings. The observation of the crossover from the 3D
                      electronic transport regime for small spacings between the
                      probesto the 2D regime for large spacings enables the
                      determination of both in-plane and perpendicular-to-plane
                      resistivities. After working out the analytical description
                      of the method, the experimental procedures for measuring
                      electronic transport properties witha multi-probe scanning
                      tunneling microscope are described, in particular the
                      influences of sample size and shape, surface morphology and
                      grain size, probe-sample contact sizeand as well as the main
                      experimental error sources. [...]},
      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/875393},
}