Conductivity in Ferroelectric Barium Titanate: Electrons Versus Oxygen Vacancies

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 68; no. 2; pp. 296 - 302
• Main Author: Tyunina, M.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.02.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustics; Barium titanates; Conductivity; Electric fields; Electrical resistivity; ferroelectric (FE) devices; Ferroelectric materials; Ferroelectricity; Frequency control; Hypotheses; Iron; Oxygen; Perovskites; Semiconductor device measurement; Temperature measurement; Vacancies
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2020.2978901

Mobile oxygen vacancies are increasingly widely believed to be responsible for electrical conductivity in perovskite oxide ferroelectrics. Here, this hypothesis is debated. The small-signal conductivity is investigated in oxygen-deficient films of barium titanate, where oxygen vacancies are epitaxially clamped and immobile. The observed behavior of conductivity as a function of temperature and frequency evidences pure electronic processes. Importantly, it is shown that these processes mimic motion of oxygen vacancies, which are immobile. It is also demonstrated that under the applied dc electric field, the electronic processes lead to such effects as coloration and degradation, which before were plausibly ascribed to migration of oxygen vacancies. Finally, it is concluded that the hypothesis of mobile oxygen vacancies is misleading.