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@ARTICLE{Wedig:276083,
      author       = {Wedig, Anja and Lübben, Michael and Cho, Deok-Yong and
                      Moors, Marco and Skaja, Katharina and Rana, Vikas and
                      Hasegawa, Tsuyoshi and Adepalli, Kiran K. and Yildiz, Bilge
                      and Waser, R. and Valov, Ilia},
      title        = {{N}anoscale cation motion in {T}a{O}$_{x}$, {H}f{O}$_{x}$
                      and {T}i{O}$_{x}$ memristive systems},
      journal      = {Nature nanotechnology},
      volume       = {11},
      issn         = {1748-3395},
      address      = {London [u.a.]},
      publisher    = {Nature Publishing Group},
      reportid     = {FZJ-2015-06569},
      pages        = {67-74},
      year         = {2016},
      abstract     = {A detailed understanding of the resistive switching
                      mechanisms that operate in redox-based resistive
                      random-access memories (ReRAM) is key to controlling these
                      memristive devices and formulating appropriate design rules.
                      Based on distinct fundamental switching mechanisms, two
                      types of ReRAM have emerged: electrochemical metallization
                      memories, in which the mobile species is thought to be metal
                      cations, and valence change memories, in which the mobile
                      species is thought to be oxygen anions (or positively
                      charged oxygen vacancies). Here we show, using scanning
                      tunnelling microscopy and supported by potentiodynamic
                      current–voltage measurements, that in three typical
                      valence change memory materials (TaOx, HfOx and TiOx) the
                      host metal cations are mobile in films of 2 nm thickness.
                      The cations can form metallic filaments and participate in
                      the resistive switching process, illustrating that there is
                      a bridge between the electrochemical metallization mechanism
                      and the valence change mechanism. Reset/Set operations are,
                      we suggest, driven by oxidation (passivation) and reduction
                      reactions. For the Ta/Ta2O5 system, a rutile-type TaO2 film
                      is believed to mediate switching, and we show that devices
                      can be switched from a valence change mode to an
                      electrochemical metallization mode by introducing an
                      intermediate layer of amorphous carbon.},
      cin          = {PGI-7},
      ddc          = {600},
      cid          = {I:(DE-Juel1)PGI-7-20110106},
      pnm          = {521 - Controlling Electron Charge-Based Phenomena
                      (POF3-521)},
      pid          = {G:(DE-HGF)POF3-521},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000367839600014},
      pubmed       = {pmid:26414197},
      doi          = {10.1038/nnano.2015.221},
      url          = {https://juser.fz-juelich.de/record/276083},
}