% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Bumer:838034,
      author       = {Bäumer, Christoph},
      title        = {{S}pectroscopic characterization of localvalence change
                      processes in resistivelyswitching complex oxides},
      volume       = {150},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-06777},
      isbn         = {978-3-95806-246-7},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {X, 206 S.},
      year         = {2017},
      note         = {RWTH Aachen, Diss., 2016},
      abstract     = {An increasingly interconnected world creates a high demand
                      for high-density and lowcost data storage. Redox-based
                      memristive devices, which allow switching between high and
                      low electrical resistances through the application of
                      voltages, are highly attractive candidates for
                      next-generation non-volatile memory. But their control and
                      rational design is complicated by poorly understood
                      switching and failure mechanisms. The complex nanoscale
                      redox processes that are suspected to drive so-called
                      resistive switching in these devices remain in adequately
                      characterized. Especially, quantitative information about
                      these processes, which is essential for further advances in
                      the educated design, has been experimentally in accessible
                      so far. Therefore, spectroscopic tools with high spatial
                      resolution are employed in this work to elucidate both
                      switching and failure mechanism of memristive devices based
                      on the model material SrTiO$_{3}$. After thorough electrical
                      characterization, two alternative photoelectron emission
                      microscopy approaches are used. As photoemission is a
                      surface sensitive process, the top electrodes of the devices
                      are removed before investigation in the first approach. In
                      the second step, thin graphene electrodes are employed,
                      enabling $\textit{in operando}$ characterization. In
                      combination with cross sectional, $\textit{in operando}$
                      transmission electron microscopy and spectroscopy, a clear
                      evidence of a reversible, localized redox reaction is
                      identied. In the low resistance state, a nanoscale lamentin
                      the SrTiO$_{3}$ is oxygen-decient, while it is nearly
                      stoichiometric in the high resistance state, resulting in a
                      valence change between Ti$^{3+}$ and Ti$^{4+}$. The carrier
                      concentration modulation resulting from this valence change
                      is quantied through comparison with calibration spectra. A
                      carrier concentration change by a factor of two causes two
                      orders of magnitude change in device resistance through a
                      modulation of the effective Schottky barrier at the
                      electrode/oxide interface. The microscopic origin of the
                      polarity of the resistance hysteresis in these devices has
                      long been debated, as it cannot be explained by the
                      typically involved purely internal redistribution of oxygen
                      vacancies. The spectroscopic results of this work reveal
                      that instead, oxygen evolution and reincorporation reactions
                      at the electrode/oxide interface are responsible for the
                      valence change in the SrTiO$_{3}$. Regarding the failure
                      mechanism, it is found that fast reoxidation frequently
                      results in retention failure in SrTiO$_{3}$ devices, which
                      can be inhibited by incidental, local phase separations.
                      Mimicking this phase separation by intentionally introducing
                      retention-stabilization layers with slow oxygen transport is
                      therefore derived as a design rule for
                      retention-failure-resistant devices.},
      cin          = {PGI-7},
      cid          = {I:(DE-Juel1)PGI-7-20110106},
      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/838034},
}