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@ARTICLE{Chen:867947,
      author       = {Chen, C. and Jost, P. and Volker, H. and Kaminski, M. and
                      Wirtssohn, M. and Engelmann, U. and Krüger, K. and Schlich,
                      F. and Schlockermann, C. and Lobo, R. P. S. M. and Wuttig,
                      M.},
      title        = {{D}ielectric properties of amorphous phase-change
                      materials},
      journal      = {Physical review / B},
      volume       = {95},
      number       = {9},
      issn         = {2469-9950},
      address      = {Woodbury, NY},
      publisher    = {Inst.},
      reportid     = {FZJ-2019-06540},
      pages        = {094111},
      year         = {2017},
      abstract     = {The dielectric function of several amorphous phase-change
                      materials has been determined by employing a combination of
                      impedance spectroscopy (9 kHz–3 GHz) and optical
                      spectroscopy from the far- (20cm−1, 0.6 THz) to the near-
                      (12000cm−1, 360 THz) infrared, i.e., from the DC limit to
                      the first interband transition. While phase-change materials
                      undergo a change from covalent bonding to resonant bonding
                      on crystallization, the amorphous and crystalline phases of
                      ordinary chalcogenide semiconductors are both governed by
                      virtually the same covalent bonds. Here, we study the
                      dielectric properties of amorphous phase-change materials on
                      the pseudobinary line between GeTe and Sb2Te3. These data
                      provide important insights into the charge transport and the
                      nature of bonding in amorphous phase-change materials. No
                      frequency dependence of permittivity and conductivity is
                      discernible in the impedance spectroscopy measurements.
                      Consequently, there are no dielectric relaxations. The
                      frequency-independent conductivity is in line with charge
                      transport via extended states. The static dielectric
                      constant significantly exceeds the optical dielectric
                      constant. This observation is corroborated by transmittance
                      measurements in the far infrared, which show optical
                      phonons. From the intensity of these phonon modes, a large
                      Born effective charge is derived. Nevertheless, it is known
                      that crystalline phase-change materials such as GeTe possess
                      even significantly larger Born effective charges.
                      Crystallization is hence accompanied by a huge increase in
                      the Born effective charge, which reveals a significant
                      change of bonding upon crystallization. In addition, a clear
                      stoichiometry trend in the static dielectric constant along
                      the pseudobinary line between GeTe and Sb2Te3 has been
                      identified.},
      cin          = {PGI-10},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-10-20170113},
      pnm          = {521 - Controlling Electron Charge-Based Phenomena
                      (POF3-521)},
      pid          = {G:(DE-HGF)POF3-521},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000396271400002},
      doi          = {10.1103/PhysRevB.95.094111},
      url          = {https://juser.fz-juelich.de/record/867947},
}