University of Oulu

M. Tyunina, M. Savinov, A. Dejneka; Small-polaron conductivity in perovskite ferroelectric BaTiO3 films. Appl. Phys. Lett. 14 November 2022; 121 (20): 202901.

Small-polaron conductivity in perovskite ferroelectric BaTiO₃ films

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Author: Tyunina, M.1,2; Savinov, M.2; Dejneka, A.2
Organizations: 1Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, P. O. Box 4500, FI-90014 Oulu, Finland
2Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 18221 Prague, Czech Republic
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.5 MB)
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Language: English
Published: American Institute of Physics, 2022
Publish Date: 2023-11-17


In ABO₃ perovskite oxide ferroelectrics, electrical conductivity ranges from insulator- to superconductor-type and is virtually critical for all applications of these materials. Compared to bulk ceramics and crystals, ferroelectric thin films can enable advanced control of the conductivity. Here, small-polaron hopping conductivity was evidenced and examined in various pulsed-laser-deposited films of ferroelectric BaTiO₃ and reference films of SrTiO₃. For this, AC conductivity was studied in a broad range of temperatures and frequencies for films sandwiched between the bottom and top electrodes. In the BaTiO₃ films, with increasing temperature, a significant increase in activation energy for small-polaron hopping was found and ascribed to strong electron–phonon coupling and complex lattice oscillations therein. Plain relations of the activation energy to microstructure, composition, or phase transitions were lacking, which corroborated the critical role of phonons. Additionally, a phonon-less transport was detected. It was anticipated that owing to strong electron–phonon coupling, rich phonon ensembles, and coexistence of phonon-stimulated and phonon-less processes, the small-polaron conductivity can heavily vary in ferroelectric films that necessitates further studies.

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Series: Applied physics letters
ISSN: 0003-6951
ISSN-E: 0003-6951
ISSN-L: 0003-6951
Volume: 121
Issue: 20
Article number: 202901
DOI: 10.1063/5.0129831
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
213 Electronic, automation and communications engineering, electronics
Funding: The authors acknowledge the support from the Czech Science Foundation (Grant No. 22-10832S) and the European Structural and Investment Funds and the Ministry of Education, Youth and Sports of the Czech Republic through Programme “Research, Development and Education” (Project No. SOLID21-CZ.02.1.01/0.0/0.0/16_019/0000760).
Copyright information: © 2022 Author(s). Published under an exclusive license by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in M. Tyunina, M. Savinov, A. Dejneka; Small-polaron conductivity in perovskite ferroelectric BaTiO3 films. Appl. Phys. Lett. 14 November 2022; 121 (20): 202901 and may be found at