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Infrared ellipsometry study of the confined electrons in a high-mobility γ-Al₂O₃/SrTiO₃ heterostructure

  • Yazdi-Rizi, Meghdad University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
  • Marsik, Premysl University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
  • Mallett, Benjamin P. P. University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
  • Dubroka, Adam Department of Condensed Matter Physics, Faculty of Science and Central European Institute of Technology, Masaryk University, Brno, Czech Republic
  • Christensen, D. V. Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark
  • Chen, Y. Z. Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark
  • Pryds, N. Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark
  • Bernhard, Christian University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
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    2016
Published in:
  • EPL (Europhysics Letters). - 2016, vol. 113, no. 4, p. 47005
English With infrared ellipsometry we studied the response of the confined electrons in γ-Al₂O₃/SrTiO₃ (GAO/STO) heterostructures in which they originate predominantly from oxygen vacancies. From the analysis of a so-called Berreman mode, that develops near the highest longitudinal optical phonon mode of SrTiO₃, we derive the sheet carrier density, N s , the mobility, μ, and the depth profile of the carrier concentration. Notably, we find that N s and the shape of the depth profile are similar as in LaAlO₃/SrTiO₃ (LAO/STO) heterostructures for which the itinerant carriers are believed to arise from a polar discontinuity. Despite an order of magnitude higher mobility in GAO/STO, as obtained from transport measurements, the derived mobility in the infrared range exhibits only a twofold increase. We interpret this finding in terms of the polaronic nature of the confined charge carriers in GAO/STO and LAO/STO which leads to a strong, frequency-dependent interaction with the STO phonons.
Faculty
Faculté des sciences et de médecine
Department
Département de Physique
Language
  • English
Classification
Physics
License
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Persistent URL
https://folia.unifr.ch/unifr/documents/304881
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