Journal article

Terahertz ellipsometry study of the soft mode behavior in ultrathin SrTiO films

  • Marsik, Premysl Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Sen, Kaushik Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Khmaladze, Jarji Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Yazdi-Rizi, Meghdad Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Mallett, Benjamin P. P. Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
  • Bernhard, Christian Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Switzerland
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    01.02.2016
Published in:
  • Applied Physics Letters. - 2016, vol. 108, no. 5, p. 052901
English We present a combined study with time-domain terahertz and conventional far-infrared ellipsometry of the temperature dependent optical response of SrTiO₃thin films (82 and 8.5 nm) that are grown by pulsed-laser deposition on (La0.3Sr0.7) (Al0.65Ta0.35)O₃ (LSAT) substrates. We demonstrate that terahertz ellipsometry is very sensitive to the optical response of these thin films, in particular, to the soft mode of SrTiO₃. We show that for the 82 nm film the eigenfrequency of the soft mode is strongly reduced by annealing at 1200 °C, whereas for the 8.5 nm film it is hardly affected. For the latter, after annealing the mode remains at 125 cm⁻¹ at 300 K and exhibits only a weak softening to about 90 cm⁻¹ at 10 K. This suggests that this ultrathin film undergoes hardly any relaxation of the compressive strain due to the LSAT substrate.
Faculty
Faculté des sciences et de médecine
Department
Département de Physique
Language
  • English
Classification
Physics
License
License undefined
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Persistent URL
https://folia.unifr.ch/unifr/documents/305194
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