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@ARTICLE{Ostapchuk:32287,
      author       = {Ostapchuk, T. and Petzelt, J. and Zelezny, V. and Pashkin,
                      A. and Pokorny, J. and Drbohlav, I. and Kuzel, R. and
                      Rafaja, D. and Gorshunov, B. P. and Dressel, M. and Ohly,
                      Ch. and Hoffmann-Eifert, S. and Waser, R.},
      title        = {{O}rigin of soft-mode stiffening and reduced dielectric
                      response in {S}r{T}i{O}3 thin films},
      journal      = {Physical review / B},
      volume       = {66},
      number       = {23},
      issn         = {0163-1829},
      address      = {College Park, Md.},
      publisher    = {APS},
      reportid     = {PreJuSER-32287},
      pages        = {235406},
      year         = {2002},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {The problem of the reduced dielectric response in thin
                      films of high-permittivity materials is analyzed by studying
                      the soft-mode response in several SrTiO3 thin films by means
                      of Fourier transform far infrared, monochromatic
                      submillimeter, and micro-Raman spectroscopies. A
                      300-nm-thick metalorganic chemical vapor deposition film,
                      quasiepitaxially grown on a (0001) sapphire substrate with a
                      perfect <111> orientation, displays a ferroelectric
                      transition near 125 K induced by a tensile residual stress,
                      appearing apparently simultaneously with the
                      antiferrodistortive transition. On the other hand,
                      polycrystalline chemical solution deposition films grown on
                      (0001) sapphire, and also tensile stressed, show a harder
                      soft mode response without the appearance of macroscopic
                      ferroelectricity. This effect, which increases with the film
                      thickness, is explained by a strong depolarizing field
                      induced by the percolated porosity and cracks (in the 10-nm
                      scale) along the boundaries of columnar grains (normal to
                      the probe field direction). Brick-wall model calculations
                      showed that 0.2 vol. $\%$ of such a porosity type reduces
                      the permittivity from 30000 to less than 1000. The
                      activation of the forbidden IR modes in the Raman spectra in
                      the whole 80-300-K temperature range studied is explained by
                      the effect of polar grain boundaries, in analogy with the
                      bulk ceramics.},
      keywords     = {J (WoSType)},
      cin          = {IFF-EKM},
      ddc          = {530},
      cid          = {I:(DE-Juel1)VDB35},
      pnm          = {Materialien, Prozesse und Bauelemente für die Mikro- und
                      Nanoelektronik},
      pid          = {G:(DE-Juel1)FUEK252},
      shelfmark    = {Physics, Condensed Matter},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000180279400097},
      doi          = {10.1103/PhysRevB.66.235406},
      url          = {https://juser.fz-juelich.de/record/32287},
}