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

Winkler, Christopher; Jablonski, Michael L.; Ashraf, Khalid; Damodaran, Anoop R.; Jambunathan, K.; Hart, James L.; Wen, Jianguo; Miller, Dean J.; Martin, Lane W.; Salahuddin, Sayeef; Taheri, Mitra L.

doi:10.1021/nl501304e

Cited by 15 publications

(32 citation statements)

References 34 publications

(57 reference statements)

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“…In the field of simulations, the community has developed innovative ways to emulate many aspects of in operando conditions, including how changes in surface composition, defect concentration, epitaxial strain, interfacial effects and other factors affect the evolution of complex systems. Today it is possible to probe the role of compositional disorder on the temporal-and spatial-dependent dielectric response of very complex relaxor materials and other ferroelectrics using advanced molecular dynamics simulations with extremely large supercells 19,[238][239][240][241] correction and 4D approaches) provide unprecedented atomic-scale insight and are beginning to be able to probe ferroelectrics at the timescales at which real processes, which are important for device operation, happen [242][243][244][245] .…”

Section: Real-time Studies Of Ferroelectrics and Devicesmentioning

confidence: 99%

Thin-film ferroelectric materials and their applications

2016

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| Ferroelectric materials, because of their robust spontaneous electrical polarization, are widely used in various applications. Recent advances in modelling, synthesis and characterization techniques are spurring unprecedented advances in the study of these materials. In this Review, we focus on thin-film ferroelectric materials and, in particular, on the possibility of controlling their properties through the application of strain engineering in conventional and unconventional ways. We explore how the study of ferroelectric materials has expanded our understanding of fundamental effects, enabled the discovery of novel phases and physics, and allowed unprecedented control of materials properties. We discuss several exciting possibilities for the development of new devices, including those in electronic, thermal and photovoltaic applications, and transduction sensors and actuators. We conclude with a brief survey of the different directions that the field may expand to over the coming years. REVIEWS NATURE REVIEWS | MATERIALS VOLUME 2 | ARTICLE NUMBER 16087 | 1 © 2 0 1 7 M a c m i l l a n P u b l i s h e r s L i m i t e d , p a r t o f S p r i n g e r N a t u r e . A l l r i g h t s r e s e r v e d .

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Section: Real-time Studies Of Ferroelectrics and Devicesmentioning

confidence: 99%

Thin-film ferroelectric materials and their applications

2016

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“…Despite the common belief of dislocations globally acting as pinning sites and the authors' previous work indicating that dislocations can globally affect the switching behavior, our observations reveal that only certain dislocation orientations affect the local domain-wall motion. 26 Specifically, dislocations running through the long axis (see Domain 8 in Figure 4) do not seem to have a noticeable effect, while perpendicular dislocations (see Domain 3, 4, and 7 in Figure 4) appear to influence it greatly. Cartoon schematics showing the idealized domain motion along with the effects of nonidealized cases with dislocations at orientations are shown to help guide the eye ( Figure 5).…”

Section: ■ Experimental and Modeling Proceduresmentioning

confidence: 96%

“…26,30,31 Bias is applied via embedded SrRuO 3 electrodes along [110] as described in previous work, with the bias applied 45°to the long axes of the domain variants present. 26,30,31 The bias-direction dependence of the domainwall motion and the influence of zero-and one-dimensional defects are examined experimentally, while MD simulations explore the intrinsic response of defect-free ferroelastic domains under opposing bias. By a comparison of the theoretical and experimental results, the intrinsic switching behavior and the influence of defects and dislocations on the response of ferroelastic domains can be decoupled and elucidated.…”

Section: ■ Experimental and Modeling Proceduresmentioning

confidence: 99%

“…The interactions between the ferroelastic domains in BiFeO 3 and point defects and dislocations have been studied by transmission electron microscopy (TEM). 26,27,30 These defects directly affect the nucleation and relaxation of ferroelastic domains by providing a local electrostatic potential that can both pin 25 and/or assist 24 the domain-wall motion. At the same time, the stress field coupled with the dislocations can drastically change the local polarization, 28 resulting in a significant barrier for domain-wall motion.…”

Section: ■ Introductionmentioning

confidence: 99%

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Asymmetric Response of Ferroelastic Domain-Wall Motion under Applied Bias

Jablonski

Liu

Winkler

et al. 2016

ACS Appl. Mater. Interfaces

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The switching of domains in ferroelectric and multiferroic materials plays a central role in their application to next-generation computer systems, sensing applications, and memory storage. A detailed understanding of the response to electric fields and the switching behavior in the presence of complex domain structures and extrinsic effects (e.g., defects and dislocations) is crucial for the design of improved ferroelectrics. In this work, in situ transmission electron microscopy is coupled with atomistic molecular dynamics simulations to explore the response of 71° ferroelastic domain walls in BiFeO3 with various orientations under applied electric-field excitation. We observe that 71° domain walls can have intrinsically asymmetric responses to opposing biases. In particular, when the electric field has a component normal to the domain wall, forward and backward domain-wall velocities can be dramatically different for equal and opposite fields. Additionally, the presence of defects and dislocations can strongly affect the local switching behaviors through pinning or nucleation of the domain walls. These results offer insight for controlled ferroelastic domain manipulation via electric-field engineering.

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Electron Beam Induced Domain Motion in Ferroelectric RKTP Observed By Transmission Electron Microscopy

2015

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Utilization of ferroelectrics for practical applications requires precise control of domain structure, thus ferroelectric domain behavior is a widely researched area. In-situ transmission electron microscopy (TEM) is an increasingly popular tool for studying domain dynamics at high spatial and temporal resolution [1]- [3]. In this technique domain behavior is studied as a function of an applied electric field, however, the TEM's electron beam alone can induce ferroelectric domain motion independent of the applied field. Here we present electron beam induced domain motion in the uniaxial ferroelectric Rb doped KTiOPO 4 (RKTP), using a JEOL 2100 LaB 6 TEM operated at 200 keV. This process is dependent on both the sample geometry and electron beam conditions. By manipulating the electron beam we can control the direction of domain propagation, and by using a condensed probe we can locally nucleate domains.In TEM a negligible amount of beam electrons are trapped within the sample volume. Charging occurs due to Auger and secondary electron emission after inelastic scattering interactions [4]. For a conducting sample, charging is alleviated through compensating electric currents, but for an insulating material such as RKTP, large positive charge can accumulate beneath the electron beam leading to strong internal fields.RKTP samples were prepared using a focused ion beam (FIB). All images shown here are DF images of 001 type reflections ( Figure 1A). Initial domain morphology is shown in Figure 1B. Pre-existing domains are present, extending across the length of the sample with domain walls parallel to the c-axis (ferroelectric axis). When the sample is uniformly illuminated under the electron beam, the entire sample develops a positive charge. Because these samples were prepared in the FIB, there is a layer of conducting platinum on the top edge of the lift-outs. This metallic contact locally alleviates charging, leading to non-uniform charge build-up and a resultant internal electric field pointing towards the metal contact. This field acts to shrink pre-existing c-domains (Figures 2A and 2B). Conversely, if the specimen is non-uniformly illuminated so that only the top half of the sample is under the beam, only the top section positively charges, leading to an electric field pointing away from the top metal contact. Under such conditions we see nucleation and propagation of domains from the bottom of the sample up ( Figure 2C). When the beam is condensed to a fine probe and placed in a mono-domain area ( Figure 3A), only the illuminated region charges. The resultant electric field points radially away from the illuminated area. Because RKTP is a uniaxial ferroelectric, there is a single direction where the field is aligned with the ferroelectric axis allowing for domain nucleation. Under condensed beam conditions, we see domain nucleation at the perimeter of the electron beam ( Figure 3B). This is the expected result as the beam perimeter has the highest charge density gradient and thus the strongest electric field ...

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

Cited by 15 publications

References 34 publications

Thin-film ferroelectric materials and their applications

Thin-film ferroelectric materials and their applications

Asymmetric Response of Ferroelastic Domain-Wall Motion under Applied Bias

Electron Beam Induced Domain Motion in Ferroelectric RKTP Observed By Transmission Electron Microscopy

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