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DF: Fachverband Dielektrische Festkörper
DF 17: Ferroics - Domains, Domain Walls and Skyrmions IV
DF 17.9: Topical Talk
Donnerstag, 23. März 2017, 12:15–12:45, WIL B321
Role of charged defects on conduction and dynamics of domain walls in BiFeO3 — •Tadej Rojac1, Andreja Bencan2, Goran Drazic2, Naonori Sakomoto2, Hana Ursic2, Bostian Jancar2, Gasper Tavcar2, Maja Makarovic2, Julian Walker2, Barbara Malic2, and Dragan Damjanovic2 — 1Electronic Ceramics Department, Jozef Stefan Institute, 1000 Ljubljana, Slovenia — 2See author list of the paper in Nature Materials
Domain walls in ferroelectrics tend to interact with charged point defects, such as oxygen vacancies, resulting in pinning effects. In practice, this "hardening" mechanism represents one of the most important ways of controlling properties in ferroelectrics. For example, doping Pb(Zr,Ti)O3 or BaTiO3 with an acceptor will create oxygen vacancies which by forming re-orientable defect complexes act as pinning sites for domain walls, affecting profoundly the switching behavior and piezoelectric response. It is widely accepted that oxygen vacancies play the major role in pinning effects and hardening. It has been recently established that undoped polycrystalline BiFeO3 behaves as a "hard" ferroelectric. Using atomic-scale structural and chemical analysis, we will show that, in contrast to the usually assumed oxygen vacancies, the dominant defects in BiFeO3 mainly responsible for the pinning effect are electron holes, associated with the presence of Fe4+, and bismuth vacancies. Direct identification of these charged defects using Cs-corrected microscopy also showed that they have a tendency to accumulate in the domain wall region, revealing the p-type hopping conduction at domain walls associated with Fe4+ defects. Discussion will be provided on how this local conductivity affects domain-wall dynamics and thus the piezoelectric response of BiFeO3.
Rojac, Tadej, et al. "Domain-wall conduction in ferroelectric BiFeO3 controlled by accumulation of charged defects." Nature Materials (2016)