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@ARTICLE{Kellner:841205,
      author       = {Kellner, J. and Bihlmayer, G. and Deringer, V. L. and
                      Liebmann, M. and Pauly, C. and Giussani, A. and Boschker, J.
                      E. and Calarco, R. and Dronskowski, R. and Morgenstern, M.},
      title        = {{E}xploring the subsurface atomic structure of the
                      epitaxially grown phase-change material {G}e2 {S}b2 {T}e5},
      journal      = {Physical review / B},
      volume       = {96},
      number       = {24},
      issn         = {2469-9950},
      address      = {Woodbury, NY},
      publisher    = {Inst.},
      reportid     = {FZJ-2017-08298},
      pages        = {245408},
      year         = {2017},
      abstract     = {Scanning tunneling microscopy (STM) and spectroscopy (STS)
                      in combination with density functional theory (DFT)
                      calculations are employed to study the surface and
                      subsurface properties of the metastable phase of the
                      phase-change material Ge2Sb2Te5 as grown by molecular beam
                      epitaxy. The (111) surface is covered by an intact Te layer,
                      which nevertheless permits the detection of the more
                      disordered subsurface layer made of Ge and Sb atoms.
                      Centrally, we find that the subsurface layer is
                      significantly more ordered than expected for metastable
                      Ge2Sb2Te5. First, we show that vacancies are nearly absent
                      within the subsurface layer. Secondly, the potential
                      fluctuation, tracked by the spatial variation of the valence
                      band onset, is significantly less than expected for a random
                      distribution of atoms and vacancies in the subsurface layer.
                      The strength of the fluctuation is compatible with the
                      potential distribution of charged acceptors without being
                      influenced by other types of defects. Thirdly, DFT
                      calculations predict a partially tetrahedral Ge bonding
                      within a disordered subsurface layer, exhibiting a clear
                      fingerprint in the local density of states as a peak close
                      to the conduction band onset. This peak is absent in the STS
                      data implying the absence of tetrahedral Ge, which is likely
                      due to the missing vacancies required for structural
                      relaxation around the shorter tetrahedral Ge bonds. Finally,
                      isolated defect configurations with a low density of
                      10−4nm−2 are identified by comparison of STM and DFT
                      data, which corroborates the significantly improved order in
                      the epitaxial films driven by the buildup of vacancy
                      layers.},
      cin          = {PGI-1 / IAS-1 / JARA-FIT / JARA-HPC},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-1-20110106 / I:(DE-Juel1)IAS-1-20090406 /
                      $I:(DE-82)080009_20140620$ / $I:(DE-82)080012_20140620$},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)
                      / Magnetic Anisotropy of Metallic Layered Systems and
                      Nanostructures $(jiff13_20131101)$},
      pid          = {G:(DE-HGF)POF3-143 / $G:(DE-Juel1)jiff13_20131101$},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000417639900007},
      doi          = {10.1103/PhysRevB.96.245408},
      url          = {https://juser.fz-juelich.de/record/841205},
}