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@ARTICLE{Schroeder:202060,
      author       = {Schroeder, Herbert},
      title        = {{P}oole-{F}renkel-effect as dominating current mechanism in
                      thin oxide films—{A}n illusion?!},
      journal      = {Journal of applied physics},
      volume       = {117},
      number       = {21},
      issn         = {1089-7550},
      address      = {Melville, NY},
      publisher    = {American Inst. of Physics},
      reportid     = {FZJ-2015-04349},
      pages        = {215103 -},
      year         = {2015},
      abstract     = {In many of the publications, over 50 per year for the last
                      five years, the Poole-Frenkel-effect (PFE) is identified or
                      suggested as dominating current mechanism to explain
                      measured current–electric field dependencies in
                      metal-insulator-metal (MIM) thin film stacks. Very often,
                      the insulating thin film is a metal oxide as this class of
                      materials has many important applications, especially in
                      information technology. In the overwhelming majority of the
                      papers, the identification of the PFE as dominating current
                      mechanism is made by the slope of the current–electric
                      field curve in the so-called Poole-Frenkel plot, i.e.,
                      logarithm of current density, j, divided by the applied
                      electric field, F, versus the square root of that field.
                      This plot is suggested by the simplest current equation for
                      the PFE, which comprises this proportionality (ln(j/F) vs. F
                      1/2) leading to a straight line in this plot. Only one other
                      parameter (except natural constants) may influence this
                      slope: the optical dielectric constant of the insulating
                      film. In order to identify the importance of the PFE
                      simulation studies of the current through MIM stacks with
                      thin insulating films were performed and the
                      current–electric field curves without and with
                      implementation of the PFE were compared. For the simulation,
                      an advanced current model has been used combining electronic
                      carrier injection/ejection currents at the interfaces,
                      described by thermionic emission, with the carrier transport
                      in the dielectric, described by drift and diffusion of
                      electrons and holes in a wide band gap semiconductor.
                      Besides the applied electric field (or voltage), many other
                      important parameters have been varied: the density of the
                      traps (with donor- and acceptor-like behavior); the
                      zero-field energy level of the traps within the energy gap,
                      this energy level is changed by the PFE (also called
                      internal Schottky effect); the thickness of the dielectric
                      film; the permittivity of the dielectric film simulating
                      different oxide materials; the barriers for electrons and
                      holes at the interfaces simulating different electrode
                      materials; the temperature. The main results and conclusions
                      are: (1) For a single type of trap present only (donor-like
                      or acceptor-like), none of the simulated current density
                      curves shows the expected behavior of the PFE and in most
                      cases within the tested parameter field the effect of PFE is
                      negligibly small. (2) For both types of traps present
                      (compensation) only in the case of exact compensation, the
                      expected slope in the PF-plot was nearly found for a wider
                      range of the applied electric field, but for a very small
                      range of the tested parameter field because of the very
                      restricting additional conditions: first, the quasi-fermi
                      level of the current controlling particle (electrons or
                      holes) has to be 0.1 to 0.5 eV closer to the respective
                      band limit than the zero-field energy level of the
                      respective traps and, second, the compensating trap energy
                      level has to be shallow. The conclusion from all these
                      results is: the observation of the PFE as dominating current
                      mechanism in MIM stacks with thin dielectric (oxide) films
                      (typically 30 nm) is rather improbable!},
      cin          = {PGI-7},
      ddc          = {530},
      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:000355925600060},
      doi          = {10.1063/1.4921949},
      url          = {https://juser.fz-juelich.de/record/202060},
}