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@ARTICLE{Aslam:155285,
      author       = {Aslam, N. and Longo, V. and Rodenbücher, C. and Roozeboom,
                      F. and Kessels, W. M. M. and Szot, K. and Waser, R. and
                      Hoffmann-Eifert, S.},
      title        = {{I}mpact of composition and crystallization behavior of
                      atomic layer deposited strontium titanate films on the
                      resistive switching of {P}t/{STO}/{T}i{N} devices},
      journal      = {Journal of applied physics},
      volume       = {116},
      number       = {6},
      issn         = {1089-7550},
      address      = {Melville, NY},
      publisher    = {American Institute of Physics},
      reportid     = {FZJ-2014-04458},
      pages        = {064503 -},
      year         = {2014},
      abstract     = {The resistive switching (RS) properties of strontium
                      titanate (Sr1+xTi1+yO3+(x+2y), STO) based metal-oxide-metal
                      structures prepared from industrial compatible processes
                      have been investigated focusing on the effects of
                      composition, microstructure, and device size. Metastable
                      perovskite STO films were prepared on Pt-coated Si
                      substrates utilizing plasma-assisted atomic layer deposition
                      (ALD) from cyclopentadienyl-based metal precursors and
                      oxygen plasma at 350 °C, and a subsequent annealing at
                      600 °C in nitrogen. Films of 15 nm and 12 nm
                      thickness with three different compositions
                      [Sr]/([Sr] + [Ti]) of 0.57 (Sr-rich STO), 0.50
                      (stoichiometric STO), and 0.46 (Ti-rich STO) were integrated
                      into Pt/STO/TiN crossbar structures with sizes ranging from
                      100 μm2 to 0.01 μm2. Nano-structural characterizations
                      revealed a clear effect of the composition of the
                      as-deposited STO films on their crystallization behavior and
                      thus on the final microstructures. Local current maps
                      obtained by local-conductivity atomic force microscopy were
                      in good agreement with local changes of the films'
                      microstructures. Correspondingly, also the initial leakage
                      currents of the Pt/STO/TiN devices were affected by the STO
                      compositions and by the films' microstructures. An
                      electroforming process set the Pt/STO/TiN devices into the
                      ON-state, while the forming voltage decreased with
                      increasing initial leakage current. After a RESET process
                      under opposite voltage has been performed, the Pt/STO/TiN
                      devices showed a stable bipolar RS behavior with non-linear
                      current-voltage characteristics for the high (HRS) and the
                      low (LRS) resistance states. The obtained switching polarity
                      and nearly area independent LRS values agree with a
                      filamentary character of the RS behavior according to the
                      valence change mechanism. The devices of 0.01 μm2 size
                      with a 12 nm polycrystalline stoichiometric STO film were
                      switched at a current compliance of 50 μA with voltages
                      of about ±1.0 V between resistance states of about
                      40 kΩ (LRS) and 1 MΩ (HRS). After identification of the
                      influences of the films' microstructures, i.e., grain
                      boundaries and small cracks, the remaining RS properties
                      could be ascribed to the effect of the
                      [Sr]/([Sr] + [Ti]) composition of the ALD STO thin
                      films.},
      cin          = {PGI-7},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-7-20110106},
      pnm          = {424 - Exploratory materials and phenomena (POF2-424)},
      pid          = {G:(DE-HGF)POF2-424},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000341179400059},
      doi          = {10.1063/1.4891831},
      url          = {https://juser.fz-juelich.de/record/155285},
}