Polar phonon behaviour in polycrystalline Bi-doped strontium titanate thin films

0547505 - FZÚ 2022 RIV CH eng J - Journal Article
Tkach, A. - Okhay, O. - Nuzhnyy, Dmitry - Petzelt, Jan - Vilarinho, P. M.
Polar phonon behaviour in polycrystalline Bi-doped strontium titanate thin films.
Materials. Roč. 14, č. 21 (2021), č. článku 6414. E-ISSN 1996-1944
R&D Projects: GA MŠMT(CZ) EF16_019/0000760; GA ČR(CZ) GA21-06802S
Grant - others:OP VVV - SOLID21(XE) CZ.02.1.01/0.0/0.0/16_019/0000760
Institutional support: RVO:68378271
Keywords : perovskites * polar dielectrics * thin films * infrared spectroscopy
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 3.748, year: 2021
Method of publishing: Open access

We study the lattice dynamics in sol–gel-derived Sr1−1.5xBixTiO3 thin films with x = 0.0053 and 0.167, deposited on Al2O3 substrates, using a variable-temperature far-infrared spectroscopy in a transmittance mode. Bi doping, known to induce a low-frequency dielectric relaxation in SrTiO3 (ST) ceramics and films, due to off-centre dopant ion displacements generating electric dipoles, is shown to affect the polar phonon behaviour of thin films. We show that in weakly Bi-doped films, the low-frequency polar TO1 mode softens on cooling but less than in undoped ST. In heavily Bi-doped ST films, this mode displays no significant frequency variation with temperature from 300 to 10 K. The polar phonon behaviour of polycrystalline Bi-doped ST thin films is comparable with that of Bi-doped ST ceramics, which exhibit dielectric relaxations and harden soft-mode behaviour instead of the ferroelectric phase transition.
Permanent Link: http://hdl.handle.net/11104/0323880