Abstract
Switching dynamics of ferroelectric materials are governed by the response of domain walls to applied electric field. In epitaxial ferroelectric films, thermally-activated ‘creep’ motion plays a significant role in domain wall dynamics, and accordingly, detailed understanding of the system’s switching properties requires that this creep motion be taken into account. Despite this importance, few studies have investigated creep motion in ferroelectric films under ac-driven force. Here, we explore ac hysteretic dynamics in epitaxial BiFeO3 thin films, through ferroelectric hysteresis measurements, and stroboscopic piezoresponse force microscopy. We reveal that identically-fabricated BiFeO3 films on SrRuO3 or La0.67Sr0.33MnO3 bottom electrodes exhibit markedly different switching behaviour, with BiFeO3/SrRuO3 presenting essentially creep-free dynamics. This unprecedented result arises from the distinctive spatial inhomogeneities of the internal fields, these being influenced by the bottom electrode’s surface morphology. Our findings further highlight the importance of controlling interface and defect characteristics, to engineer ferroelectric devices with optimised performance.
Highlights
Switching dynamics of ferroelectric materials are governed by the response of domain walls to applied electric field
polarization-electric field (P-E) loops measured on Pt/BFO/LSMO capacitors (Fig. 1b) are strongly frequency dependent: higher frequencies induce a decrease in the slope dP/dE, and an increase in the that it scales as a coercive field EC
A domain wall cannot overcome the depinning energy from a pinning site before the external ac field changes its polarity. Using this general framework of pinning-dominated dynamics in a ferroic system, we have extended this theory to explain our present observations
Summary
Switching dynamics of ferroelectric materials are governed by the response of domain walls to applied electric field. Thermally-activated ‘creep’ motion plays a significant role in domain wall dynamics, and detailed understanding of the system’s switching properties requires that this creep motion be taken into account. We reveal that identicallyfabricated BiFeO3 films on SrRuO3 or La0.67Sr0.33MnO3 bottom electrodes exhibit markedly different switching behaviour, with BiFeO3/SrRuO3 presenting essentially creep-free dynamics This unprecedented result arises from the distinctive spatial inhomogeneities of the internal fields, these being influenced by the bottom electrode’s surface morphology. (For ferroelectric domain walls, E corresponds to external electric field.) Above a critical driving force EC0, a depinning transition occurs After this transition, the objects have an average velocity v that is linearly proportional to E; this is the flow regime. EC0 represents a dynamic threshold field at zero temperature. (b) Room-temperature polarization-electric field (P-E)
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