Accessing intermediate ferroelectric switching regimes with time-resolved transmission electron microscopy

Abstract

Piezoresponse force microscopic study of ferroelectric (1−x)Pb(Sc1/2Nb1/2)O3−xPbTiO3 and Pb(Sc1/2Nb1/2)O3 single crystals J. Appl. Phys. 112, 052009 (2012) Piezoresponse force microscopy studies on the domain structures and local switching behavior of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals J. Appl. Phys. 112, 052006 (2012) Antiferroelectric-like properties and enhanced polarization of Cu-doped K0.5Na0.5NbO3 piezoelectric ceramics Appl. Phys. Lett. 101, 082901 (2012) BiFeO 3 (BFO) is one of the most widely studied magneto-electric multiferroics. The magnetoelectric coupling in BiFeO 3 , which allows for the control of the ferroelectric and magnetic domain structures via applied electric fields, can be used to incorporate BiFeO 3 into novel spintronics devices and sensors. Before BiFeO 3 can be integrated into such devices, however, a better understanding of the dynamics of ferroelectric switching, particularly in the vicinity of extended defects, is needed. We use in situ transmission electron microscopy (TEM) to investigate the response of ferroelectric domains within BiFeO 3 thin films to applied electric fields at high temporal and spatial resolution. This technique is well suited to imaging the observed intermediate ferroelectric switching regimes, which occur on a time-and length-scale that are too fine to study via conventional scanning-probe techniques. Additionally, the spatial resolution of transmission electron microscopy allows for the direct study of the dynamics of domain nucleation and propagation in the presence of structural defects. In this article, we show how this high resolution technique captures transient ferroelectric structures forming during biasing, and how defects can both pin domains and act as a nucleation source. The observation of continuing domain coalescence over a range of times qualitatively agrees with the nucleation-limited-switching model proposed by Tagantsev et al. We demonstrate that our in situ transmission electron microscopy technique is well-suited to studying the dynamics of ferroelectric domains in BiFeO 3 and other ferroelectric materials. These biasing experiments provide a real-time view of the complex dynamics of domain switching and complement scanning-probe techniques. V C 2012 American Institute of Physics. [http://dx

Real-Time Observation of Local Strain Effects on Nonvolatile Ferroelectric Memory Storage Mechanisms

“…The work presented herein provides insight into the switching behavior of devices containing significant defect densities and directly shows the interactions between dislocations and domain walls, revealing a preference for domain nucleation to locally follow the NLS model over the KAI model, while the global behavior follows the KAI model. 17 The results prove that the direct impact of strain and defects is a crucial factor for determining the appropriate switching mechanism for ferroelectric domains in nanoscale device architectures.…”

“…10−16 Both theoretical and experimental studies have shown that strain fields around threading dislocations result in ∼1 nm "dead" areas (near-zero polarization), which pin domain walls. 10,16,17 Variations in Burger's vectors of misfit or threading dislocations have also been shown to alter local domain morphology and nucleation behavior. 12 While the KAI model is typically used to describe domain switching in bulk and microscale ferroelectrics, the NLS model has been found to better fit thin-film devices and nanoscale capacitors.…”

Atomic-scale mechanisms of ferroelastic domain-wall-mediated ferroelectric switching

“…In comparison with general measurement techniques, in situ TEM can be used to directly observe atomicscale domain interactions in real time during switching through the thickness of the film, enabling switching dynamics to be correlated with local defect microstructures in real time 13,18,19 . Employing spherical aberration-corrected TEM with sub-angstrom resolution 20,21 , we are able to directly map the local polarization at the atomic scale [9][10] .…”

Studies on structural, electrical and magnetic properties of Dy-doped BiFeO3 thin films

“…Multiferroic materials exhibit the simultaneous existence of at least two of the ferroelectric, ferromagnetic, and ferroelastic coupled order parameters within a single phase in a certain range of temperatures [1,2]. They have recently attracted much attention due to the promising multifunctional device applications in information storage, sensor, spintronics, multi-states memory, etc.…”