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@PHDTHESIS{Sommer:988396,
      author       = {Sommer, Nils},
      othercontributors = {Waser, Rainer and Jungemann, Christoph},
      title        = {{M}odeling and simulation of bilayer area-dependent valence
                      change memory devices},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2024-06154},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2024},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, Rheinisch-Westfälische Technische
                      Hochschule Aachen, 2024},
      abstract     = {The development of future semiconductor devices brings
                      major challenges. Moore's famous law has predicted the
                      miniaturization for decades. However, current technologies
                      are reaching their physical limits. Further, the increasing
                      number of computer technologies worldwide requires more and
                      more electrical energy. Therefore, new concepts are
                      proposed, e.g., Redox-based Random Access Memory (ReRAM),
                      in-memory computing or neuromorphic applications. In this
                      context, valence change memory cells (VCM) are promising
                      candidates for the implementations of these concepts.
                      Area-dependent switching VCM cells are a special type of VCM
                      cells. Many of the area-dependent VCM cells consist of a
                      bilayer structure, i.e., there are two semiconducting
                      metal-oxide layers in between two metal electrodes. The
                      resistance of an area-dependent device scales linearly with
                      the device area. In addition, the resistance of the VCM cell
                      can be manipulated by applying a voltage stimuli to the
                      electrodes. It was shown experimentally that there is an
                      exchange of oxygen ions between the two metal-oxide layers
                      when the resistance of the device is changed. Hence, it was
                      suggested that this exchange is the fundamental reason for
                      the resistance change. However, this idea has been barley
                      tested by physically models so far. In this work, two
                      physically motivated models for area-dependent bilayer VCM
                      cells are developed. Both models incorporate the idea of an
                      oxygen exchange between the two metal-oxide layers. By means
                      of these models, the influence of an oxygen exchange on the
                      device resistance is investigated. Under special interest is
                      the influence of different materials parameters on the
                      resistance change as well as on the dynamically movement of
                      the oxygen ions. It is shown that device resistance can be
                      changed by the oxygen exchange. Thereby, the behavior of the
                      resistance change depends on how far the oxygen ions migrate
                      into the bulk of the materials. Further, a dependency on the
                      material permittivities is shown. Another property of
                      area-dependent VCM cells is that the resistance changes
                      gradually under applied voltages. By means of the developed
                      models it is investigated what is necessary to gain a
                      gradual change of the resistance. Furthermore, the models
                      are used for a detailed analysis of the movement of the
                      oxygen ions and how the charge carriers, i.e., electrons and
                      holes, overcome a tunnel barrier that is created by one of
                      the oxide layers. At the end of this work, the simulation
                      results are compared to experimental measurements from the
                      literature to identify which measured effects can be
                      explained by the models. In addition, it is discussed which
                      effects cannot be explained by the model of a simple oxygen
                      exchange and which extension on the models are necessary.},
      cin          = {611610},
      ddc          = {621.3},
      cid          = {$I:(DE-82)611610_20140620$},
      pnm          = {BMBF 16ME0398K - Verbundprojekt: Neuro-inspirierte
                      Technologien der künstlichen Intelligenz für die
                      Elektronik der Zukunft - NEUROTEC II - (BMBF-16ME0398K) /
                      BMBF 16ES1133K - Verbundprojekt: Neuro-inspirierte
                      Technologien der künstlichen Intelligenz für die
                      Elektronik der Zukunft - NEUROTEC -, Teilvorhaben:
                      Forschungszentrum Jülich (16ES1133K)},
      pid          = {G:(DE-82)BMBF-16ME0398K / G:(BMBF)16ES1133K},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2024-06154},
      url          = {https://publications.rwth-aachen.de/record/988396},
}