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@PHDTHESIS{Cuma:1048441,
      author       = {Cuma, David},
      othercontributors = {Voigtländer, Bert and Morgenstern, Markus},
      title        = {{M}ulti-tip scanning tunneling potentiometry on thin
                      bismuth films and topological insulators in a cryogenic
                      system},
      school       = {RWTH Aachen},
      type         = {Dissertation},
      publisher    = {RWTH Aachen University},
      reportid     = {FZJ-2025-04647},
      pages        = {pages 1 Online-Ressource : Illustrationen, Diagramme},
      year         = {2023},
      note         = {Dissertation, RWTH Aachen, 2023},
      abstract     = {A multi-tip scanning tunneling microscope (STM) is a great
                      tool to investigate charge transport properties of
                      nanostructured surfaces. This work focuses on the
                      utilization of multi-tip STM implemented scanning tunneling
                      potentiometry (STP) measurements, which allow for the
                      simultaneous acquisition of topography and potential
                      information of the sample under investigation. A detailed
                      insight into the measurement principles and setup as well as
                      theoretical considerations on this measurement method is
                      given in chapter 2. With the means of STP at hand, chapter 3
                      makes charge transport around nanoscale defects in thin
                      bismuth{012} films, which crystallize in a black phosphorus
                      like structure, the subject of discussion. Potential maps
                      recorded around those defects reveal the formation of
                      transport dipoles, which exhibit different characteristics
                      depending on the underlying transport regime. Comparing the
                      measurement data with numerical calculations and resistor
                      network simulations gives indications for the transition
                      from classical to quantum mechanical charge transport in
                      real space. The results presented in this chapter motivate
                      the need for a new STP setup at cryogenic temperatures,
                      which is introduced in chapter 4. The chapter reports a new
                      four-tip STM seated in a static bath cryostat combined with
                      a scanning electron microscope (SEM) used to monitor the tip
                      movements. Additionally, the STM's and SEM's performance
                      properties are characterized and the ultra-high vacuum
                      chamber and cryostat as well as the vibration isolation
                      system are described. Chapter 5 presents potentiometry
                      measurements in the cryogenic setup. The first part of the
                      chapter discusses thermo voltage signals in thin Bi(001) lms
                      crystallizing in a hexagonal structure. Those measurements
                      illustrate the existence of edge states depending on the
                      step edge type. Furthermore, a performance benchmark for STP
                      measurements in the setup is established. The second part of
                      the chapter characterizes the temperature dependence of
                      one-dimensional crystal defects and step edges in the
                      ternary topological insulator system (Bi1-xSbx)2Te3. It
                      demonstrates a decreased line defect conductivity at lower
                      temperatures, seemingly contradicting an increased
                      suppression of backscattering in topological surface states.
                      A suppressed backscattering can be expected at low
                      temperatures due to less multi-scattering events at crystal
                      defects.},
      cin          = {PGI-3},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-3-20110106},
      pnm          = {5213 - Quantum Nanoscience (POF4-521)},
      pid          = {G:(DE-HGF)POF4-5213},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2023-07800},
      url          = {https://juser.fz-juelich.de/record/1048441},
}