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@ARTICLE{Zurhelle:886051,
      author       = {Zurhelle, A. F. and Christensen, D. V. and Menzel, S. and
                      Gunkel, F.},
      title        = {{D}ynamics of the spatial separation of electrons and
                      mobile oxygen vacancies in oxide heterostructures},
      journal      = {Physical review materials},
      volume       = {4},
      number       = {10},
      issn         = {2475-9953},
      address      = {College Park, MD},
      publisher    = {APS},
      reportid     = {FZJ-2020-04238},
      pages        = {104604},
      year         = {2020},
      abstract     = {In the search for an oxide-based 2D electron system with a
                      large concentration of highly mobile electrons, a promising
                      strategy is to introduce electrons through donor doping
                      while spatially separating electrons and donors to prevent
                      scattering. In SrTiO3, this can be achieved by tailoring the
                      oxygen vacancy profile through reduction, e.g., by creating
                      an interface with an oxygen scavenging layer. Through
                      reduction, oxygen atoms are removed close to the interface,
                      leaving behind oxygen vacancies in the SrTiO3 lattice and
                      mobile electrons in the SrTiO3 conduction band. The commonly
                      assumed picture is that the oxygen vacancies then remain
                      confined close to the interface while the electrons leak a
                      few nanometers into the bulk, resulting in an
                      electron-defect separation and a highly mobile, oxide-based
                      2D electron system. So far it has remained unclear how the
                      confinement and electron-defect separation develop over
                      time. Here, we present transient finite element simulations
                      that consider three driving forces acting on the oxygen
                      vacancy distribution: diffusion due to the concentration
                      gradient, drift due to the intrinsic electric field, and an
                      oxygen vacancy trapping energy that holds oxygen vacancies
                      at the interface. Our simulations show that at room
                      temperature, three distinct regions are formed in SrTiO3
                      within days: (1) Oxygen vacancies are partially held at the
                      interface due to the oxygen vacancy trapping energy. (2) The
                      accompanying positive space charge causes an oxygen vacancy
                      depletion layer with large electron concentration and high
                      mobility just below the interface. This electron-defect
                      separation, indeed, leads to a highly conductive region. (3)
                      While we are able to describe measured conductivity data
                      with an oxygen vacancy trapping energy of −0.2 eV, this
                      value does not prevent oxygen vacancy diffusion into the
                      bulk: A diffusion front progresses into the bulk and leads
                      to significant conductivity arising over the first
                      micrometer within a couple of months. An enhanced oxygen
                      vacancy trapping energy of −0.5 eV or below would suppress
                      this loss of confinement, leading to a static and pronounced
                      electron-defect separation. Consequently, our results
                      highlight the importance of oxygen vacancy redistribution
                      and suggest the trapping energy of oxygen vacancies at the
                      interface as an important design parameter for
                      oxygen-vacancy-based 2D electron systems.},
      cin          = {PGI-7 / JARA-FIT},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-7-20110106 / $I:(DE-82)080009_20140620$},
      pnm          = {521 - Controlling Electron Charge-Based Phenomena
                      (POF3-521)},
      pid          = {G:(DE-HGF)POF3-521},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000582800500001},
      doi          = {10.1103/PhysRevMaterials.4.104604},
      url          = {https://juser.fz-juelich.de/record/886051},
}