Ferroelectric switching controlled by reversible elastic strain
Dr. Er-Jia Guo (Martin-Luther-University Halle-Wittenberg)

Ferroelectric ordering in complex oxide films can be very sensitive to elastic strain. This has been exploited in many strain-coupled ferroelectric thin-films, including BaTiO3, BiFeO3, Pb(Zr1-xTix)O3(PZT) and etc. The origins of strain sensitivity are multiple. Fundamentally understood and modeled strain determined processes were in rather few cases. The defects, affecting the disorder potential in the ferroelectric films, are thought to be a dominating reason to govern the domain wall creep behavior. The strain effect on the domain growth is seldom addressed due to the difficulty in comparing two defective films. We had introduce the application of piezoelectric substrates for reversible strain control in epitaxial ferroelectric films (PZT and BFO), allowing one to study the same thin film in different strain states. [1] In this talk, I will discuss the influence of reversible strain on the ferroelectric switching of BiFeO3 capacitors.[2, 3] The strain-induced relative change of the switching time is different in the low and high electric field regions, showing a crossover from slowing down at low fields to acceleration of the switching at high fields under 0.1 % of reversible compressive strain. We attribute this behavior to the difference between the dynamics of domain-wall propagation in the creep and depinning regimes.[1, 2] On the other hand, domain dynamics in BiFeO3 films under reversibly controlled elastic strain has been complementarily studied by piezoresponse force microscopy (PFM).[4] The in-plane compression significantly slows down the domain wall velocity by one order of magnitude in low field range. We attributed observed results to the enhancement of activated fields in the creep regime.
Studying the FE switching under reversible controlled strain states in various FE materials, both in capacitors and using local techniques for domain imaging, will advance the fundamental understanding of the domain switching processes.
[1] Biegalski et al. Appl. Phys. Lett. 98 (2011) 142902.
[2] E. J. Guo et al. Appl. Phys. Lett. 101 (2012) 242908.
[3] E. J. Guo et al. Appl. Phys. Lett. 103 (2013) 022905.
[4] E. J. Guo et al. submitted to Advanced Materials.
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