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@PHDTHESIS{vonWitzleben:828265,
      author       = {von Witzleben, Moritz Alexander},
      othercontributors = {Waser, Rainer and Negra, Renato},
      title        = {{S}witching kinetics of valence change memory devices on a
                      sub-100 ps timescale},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2021-09047},
      pages        = {1 Online-Ressource : Illustrationen, Diagramme},
      year         = {2021},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, Rheinisch-Westfälische Technische
                      Hochschule Aachen, 2021},
      abstract     = {The further development of today's memory technologies
                      faces several technological barriers, which yields the
                      demand for new approaches. One emerging memory type that has
                      the potential to overcome these barriers is the valence
                      change memory (VCM), which may also be usable for
                      neuromorphic applications or in-memory computations. In VCM
                      devices, the information is stored within different
                      resistive states, namely a high resistive state (HRS) and a
                      low resistive state (LRS), which can be programmed with
                      electrical stimuli. The transition from the HRS to the LRS
                      is referred to as SET and the opposite transition as RESET.
                      In this thesis, the SET and RESET times of TaOx-, ZrOx-, and
                      HfOx/TiOx-based VCM devices were studied in the time regime
                      from 50 ps to 100 ns. Signals in this time regime contain
                      high frequency components in the gigahertz regime. The
                      signals require proper impedance matching up to the VCM
                      device, which are, therefore, integrated into coplanar
                      waveguide (CPW) structures. Nevertheless, an integrated VCM
                      device constitutes a parallel plate capacitor with a
                      considerable electrical charging time, which delays the
                      measured SET and RESET times. To estimate the electrical
                      charging time, an experimental approach was used, with which
                      the time-dependent effective voltage at the VCM device could
                      be determined. This approach used the Fourier transformation
                      of the applied voltage pulse and the VCM device's scattering
                      parameters. From the resulting effective voltage at the VCM
                      device, the electrical charging time of all tested VCM
                      devices was determined. The results indicate that conducted
                      optimizations of the CPW structure decreased the electrical
                      charging time significantly and allowed fast measurements on
                      a sub-100 ps time scale. By employing dedicated hardware and
                      integrating this hardware into a software, the measurements
                      could be automated. This allowed collecting comprehensive
                      data sets on the SET and RESET kinetics of the tested VCM
                      devices and, thereby, allowed resolving their transient
                      resistance on a picosecond time scale. The measured SET
                      kinetics revealed that all studied devices can switch within
                      50 ps from the HRS to the LRS. To the author's knowledge,
                      this is the fastest switching time reported for VCM devices.
                      By comparing the SET kinetics of differently sized
                      TaOx-based VCM devices and using the determined electrical
                      charging times, it could be shown that the SET kinetics of
                      VCM devices in the subnanosecond regime are mainly limited
                      by the electrical charging time. The migration of mobile
                      donors (e.g. oxygen vacancies), which limits the SET
                      kinetics on slower time scales, and the heating time of the
                      VCM device have only a minor influence. Achieving similar
                      fast RESET times proved to be more difficult. In all studied
                      VCM devices, the coexistence of a unipolar switching mode
                      could be shown. This unipolar switching mode is triggered at
                      higher voltages, which would be required for faster RESET
                      times. Nevertheless, on some HfOx/TiOx-based VCM devices 50
                      ps fast RESET times could be measured repeatedly. From these
                      kinetics measurements, RESET programming windows could be
                      determined and, finally, approaches were derived to achieve
                      faster RESET times.},
      cin          = {611610},
      ddc          = {621.3},
      cid          = {$I:(DE-82)611610_20140620$},
      pnm          = {DFG project 167917811 - SFB 917: Resistiv schaltende
                      Chalkogenide für zukünftige Elektronikanwendungen:
                      Struktur, Kinetik und Bauelementskalierung "Nanoswitches"
                      (167917811) / BMBF-16ES1134 - Verbundprojekt:
                      Neuro-inspirierte Technologien der künstlichen Intelligenz
                      für die Elektronik der Zukunft - NEUROTEC -
                      (BMBF-16ES1134)},
      pid          = {G:(GEPRIS)167917811 / G:(DE-82)BMBF-16ES1134},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2021-09047},
      url          = {https://publications.rwth-aachen.de/record/828265},
}