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@MASTERSTHESIS{Schleenvoigt:842814,
      author       = {Schleenvoigt, Michael},
      title        = {{Q}uality {I}mprovement of {M}olecular {B}eam {E}pitaxy
                      {G}rown {T}opological {I}nsulator {T}hin {F}ilms and in situ
                      {F}abrication of {D}evices},
      school       = {RWTH Aachen University},
      type         = {Masterarbeit},
      reportid     = {FZJ-2018-01010},
      pages        = {82},
      year         = {2017},
      note         = {Masterarbeit, RWTH Aachen University, 2017},
      abstract     = {In 2005, Kane and Mele introduced topological insulators as
                      a new material class in the vast field of solid state
                      physics. Since then, research on the topic led to a plethora
                      of discoveries, ranging from two-dimensional systems to many
                      classes of three-dimensional topological insulators.
                      Topological insulators exhibit promising features, useful
                      for example for spintronic applications or quantum
                      computing. However, due to large background doping, these
                      features are often suppressed. Therefore, measures need to
                      be taken in order to lower the doping, enhancing the
                      topological characteristics.In this thesis, molecular beam
                      epitaxy grown three-dimensional topological insulators of
                      the tetradymite crystal class, consisting of bismuth,
                      antimony, tellurium and selenium (V2VI3), are investigated.
                      In the course of the work, three points of interest in a
                      conventional sample are investigated with regard to the
                      possibility to improve them. These are the interface to the
                      substrate, the bulk and the interface to the
                      environment.First, the interface of the grown film to the
                      substrate has been examined. Two approaches have been
                      pursued to influence the growth of the film. One has been
                      the use of prepatterned samples to grow topological
                      insulator films in fixed structures. The other has been
                      changing the substrate material and growing thin layers of
                      optimized films, fit to the new surfaces, as pseudo
                      substrates for subsequent growths.Next, the focus has been
                      set on the bulk of the film. In order to optimize the
                      electronic qualities of the topological insulator, a
                      quaternary material system has been grown via molecular beam
                      epitaxy. The quaternary system promises less background
                      doping and has not been grown by the means of molecular beam
                      epitaxy before.Thirdly, the interface to ambient conditions
                      has been investigated. To protect the surface of the film
                      from contaminations during ex situ processes, a technique to
                      fabricate devices in situ, the stencil lithography, has been
                      refined. The masks used for the technique have been
                      fabricated by etching onto structures patterned into silicon
                      nitride.Lastly, to conclude the two previous chapters, Hall
                      measurements have been performed on quaternary samples with
                      in situ contacts grown via the stencil lithography method.
                      The measurements have been performed at cryogenic
                      temperatures and resulted in values comparable to
                      literature.},
      cin          = {PGI-9},
      cid          = {I:(DE-Juel1)PGI-9-20110106},
      pnm          = {521 - Controlling Electron Charge-Based Phenomena
                      (POF3-521)},
      pid          = {G:(DE-HGF)POF3-521},
      typ          = {PUB:(DE-HGF)19},
      url          = {https://juser.fz-juelich.de/record/842814},
}