Doping effect of Nb on ionic polarization of SrTiO<sub>3</sub>

DOI Web Site 2 Citations 31 References Open Access
  • NISHIYAMA Junji
    Nano-Phononics Lab., School of Materials and Chemical Technology, Tokyo Institute of Technology
  • KANEHARA Kazuki
    Nano-Phononics Lab., School of Materials and Chemical Technology, Tokyo Institute of Technology
  • TAKEDA Hiroaki
    Nano-Phononics Lab., School of Materials and Chemical Technology, Tokyo Institute of Technology
  • TSURUMI Takaaki
    Nano-Phononics Lab., School of Materials and Chemical Technology, Tokyo Institute of Technology
  • HOSHINA Takuya
    Nano-Phononics Lab., School of Materials and Chemical Technology, Tokyo Institute of Technology

Abstract

<p>THz dielectric spectra of Nb-doped SrTiO3 single crystals were measured using the far-infrared spectroscopic ellipsometer to understand the doping effect of Nb on ionic polarization. The frequency of the Slater transverse optical (TO) mode increased with the doping amount of Nb, meaning the decrease in the ionic polarization by Nb doping. From the change in the Slater TO mode frequency, it was estimated that the ionic polarizability of 1% Nb-doped SrTiO3 was 10.4% lower than that of undoped SrTiO3. This result suggested that the intrinsic permittivity of Nb-doped SrTiO3 is lower than that of that of undoped SrTiO3. First principles calculations revealed that the Nb 4d-orbitals contributes to the covalency between B-site cations and O ions, however, the covalency is suppressed due to the electron carrier doping. The doped electrons causes the decrease in the long-range Coulomb force and the increase in short-range elastic force, and therefore the ionic polarizability is decreased by Nb doping.</p>

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