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@ARTICLE{Zhang:851649,
      author       = {Zhang, Hehe and Yoo, Sijung and Menzel, Stephan and Funck,
                      Carsten and Cüppers, Felix and Wouters, Dirk J. and Hwang,
                      Cheol Seong and Waser, R. and Hoffmann-Eifert, Susanne},
      title        = {{U}nderstanding the {C}oexistence of {T}wo {B}ipolar
                      {R}esistive {S}witching {M}odes with {O}pposite {P}olarity
                      in {P}t/{T}i{O} 2 /{T}i/{P}t {N}anosized {R}e{RAM}
                      {D}evices},
      journal      = {ACS applied materials $\&$ interfaces},
      volume       = {10},
      number       = {35},
      issn         = {1944-8252},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {FZJ-2018-05199},
      pages        = {29766 - 29778},
      year         = {2018},
      abstract     = {Redox-type resistive random access memories based on
                      transition-metal oxides are studied as adjustable
                      two-terminal devices for integrated network applications
                      beyond von Neumann computing. The prevailing, so-called,
                      counter-eight-wise (c8w) polarity of the switching
                      hysteresis in filamentary-type valence change mechanism
                      devices originates from a temperature- and field-controlled
                      drift-diffusion process of mobile ions, predominantly oxygen
                      vacancies in the switching oxide. Recently, a bipolar
                      resistive switching (BRS) process with opposite polarity,
                      so-called, eight-wise (8w) switching, has been reported
                      that, especially for TiO2 cells, is still not completely
                      understood. Here, we report on nanosized (<0.01 μm2)
                      asymmetric memristive cells from 3 to 6 nm thick TiO2 films
                      by atomic layer deposition, which reveal a coexistence of
                      c8w and 8w switching in the same cell. As important
                      characteristics for the studied Pt/TiO2/Ti/Pt devices, the
                      resistance states of both modes are nonvolatile and share
                      one common state; i.e., the high-resistance state of the c8w
                      mode equals the low-resistance state of the 8w-mode. A
                      transition between the opposite hysteresis loops is possible
                      by voltage control. Specifically, 8w BRS in the TiO2 cells
                      is a self-limited low-energy nonvolatile switching process.
                      Additionally, the 8w reset process enables the programming
                      of multilevel high-resistance states. Combining the
                      experimental results with data from simulation studies
                      allows to propose a model, which explains 8w BRS by an
                      oxygen transfer process across the Pt/TiO2 Schottky
                      interface at the position of the c8w filament. Therefore,
                      the coexistence of c8w and 8w BRS in the nanoscale
                      asymmetric Pt/TiO2/Ti/Pt cells is understood from a
                      competition between drift/diffusion of oxygen vacancies in
                      the oxide layer and an oxygen exchange reaction across the
                      Pt/TiO2 interface.},
      cin          = {PGI-7 / PGI-10 / JARA-FIT},
      ddc          = {540},
      cid          = {I:(DE-Juel1)PGI-7-20110106 / I:(DE-Juel1)PGI-10-20170113 /
                      $I:(DE-82)080009_20140620$},
      pnm          = {524 - Controlling Collective States (POF3-524)},
      pid          = {G:(DE-HGF)POF3-524},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:30088755},
      UT           = {WOS:000444355700059},
      doi          = {10.1021/acsami.8b09068},
      url          = {https://juser.fz-juelich.de/record/851649},
}