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@PHDTHESIS{Eschbach:811622,
      author       = {Eschbach, Markus},
      title        = {{B}and {S}tructure {E}ngineering in 3{D} {T}opological
                      {I}nsulators {I}nvestigated by {A}ngle-{R}esolved
                      {P}hotoemission {S}pectroscopy},
      volume       = {126},
      school       = {Universität Duisburg},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-04034},
      isbn         = {978-3-95806-149-1},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologie},
      pages        = {VIII, 153 S.},
      year         = {2016},
      note         = {Dissertation, Universität Duisburg, 2016},
      abstract     = {Three-dimensional topological insulators (3D TIs) are a new
                      state of quantum matter and open up fascinating
                      opportunities for novel spintronic devices due to their
                      unique electronic properties: the simultaneous presence of
                      an insulating energy gap in the bulk and conductive,
                      spin-polarized electronic states at their surface. Unlike
                      the metallic surface states of ordinary (topologically
                      trivial) materials, these (topologically non-trivial)
                      surface states are induced and protected by time reversal
                      symmetry and by a new bulk property, called topology.
                      However, for the usability of TI materials in spintronic
                      devices one needs to find means to engineer their electronic
                      band structure such that the Fermi level falls into the band
                      gap, since most of the 3D TI materials suffer from
                      significant bulk conductivity also at their surfaces. In
                      this thesis different approaches are presented to manipulate
                      the Fermi level and thereby engineer the electronic
                      properties of thin films of typical 3D TI materials, such as
                      Bi$_{2}$Se$_{3}$, Bi$_{2}$Te$_{3}$, and Sb$_{2}$Te$_{3}$,
                      which were grown by molecular beam epitaxy. Their surface
                      electronic structure is investigated using angle-resolved
                      photoelectron spectroscopy. Besides conventional approaches
                      like surface or bulk doping, the successful realization of a
                      vertical topological p-n junction in epitaxial
                      Sb$_{2}$Te$_{3}$/Bi$_{2}$Te$_{3}$/Si(111) heterostructures
                      is demonstrated for the first time. Besides the verification
                      of the crystalline quality of the bilayers and integrity of
                      the interface, it is shown that it is possible to drive the
                      surface of Sb$_{2}$Te$_{3}$ from being $\textit{p}$-type
                      into $\textit{n}$-type by varying the influence from the
                      lower Bi$_{2}$Te$_{3}$ layer, i.e. the built-in
                      electrostatic potential caused by the depletion layer. The
                      experimental findings are supported by solving the
                      Schrödinger and Poisson equations self-consistently and
                      thus simulating the band diagram throughout the
                      heterostructure. Further, a thorough investigation of the
                      crystal structure as well as the rich electronic (spin-)
                      structure of the natural superlattice phase Bi$_{1}$Te$_{1}$
                      = (Bi$_{2}$)$_{1}$(Bi$_{2}$Te$_{3}$)$_{2}$ is presented. It
                      is shown by density functional theory that Bi$_{1}$Te$_{1}$,
                      contrary to the closely related, prototypical strong 3D TI
                      Bi$_{2}$Te$_{3}$, is a weak topological insulator with
                      $v_{0}$; ($v_{1}$$v_{2}$v$_{3}$) = 0; (001). According to
                      this, surfaces, which are perpendicular to the stacking
                      direction, i.e. parallel to the natural cleavage planes, are
                      expected to be free of topological surface states. Indeed,
                      such surface is shown to exhibit surface states which in
                      fact can easily be confused with topological Dirac cones but
                      do not possess a measurable helical spin polarization which
                      thus confirms the weak topological nature of
                      Bi$_{1}$Te$_{1}$.},
      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/811622},
}