Giant flexoelectric effect through interfacial strain relaxation

Lee, Daesu; Noh, Tae Won

doi:10.1098/rsta.2012.0200

Cited by 73 publications

(59 citation statements)

References 54 publications

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“…Namely, as follows from equation (5), under the short-circuited conditions (E = 0), strain induces polarization while, as follows from equation (6), under the mechanically free conditions (σ = 0), polarization induces strain. However, equations (10) and (11) suggest a certain asymmetry between the direct and converse flexoelectric effects: as clear from equations (10) and (11), in the absence of an electric field, a strain gradient induces homogeneous polarization while, for the converse effect, in a mechanically free sample, homogeneous polarization does not induce a strain gradient. This asymmetry provoked a judgment that a sensor based on the flexoelectric effect will not behave as an actuator [7].…”

Section: Static Bulk Flexoelectric Effect-phenomenologymentioning

confidence: 99%

“…In such a situation, the role of the flexoelectricity becomes exclusive: it translates a mechanical stimulus (strain gradient) into the induced polarity of the paraelectric phase. As is clear from the constitutive equation (10), the strain gradient (due to the flexoelectricity) works as an electric field…”

Section: Internal Bias and Poling Effectmentioning

confidence: 99%

“…The goal of our treatment is to show that (100) holds 10 Here we mean a simple device based on the longitudinal piezoelectric effect, e.g. a parallel-plate capacitor homogeneously mechanically loaded.…”

Section: Blocking Boundary Conditionsmentioning

confidence: 99%

“…In the second case, a voltage V is applied between the electrodes and the displacement of the center of the plate L is measured; now, the response of the system is characterized by the factor d act = L/V. Virtually the same factors are customarily used for the characterization of a piezoelectric actuator/sensor 10 . For the piezoelectric device,…”

Section: Blocking Boundary Conditionsmentioning

confidence: 99%

“…Judging from the number of publications on flexoelectricity in solids (figure 1), the total volume of activity in the field is still modest but the field is evolving rapidly. Several reviews have already been published on flexoelectricity in solids [5][6][7][8][9][10][11][12], some of them quite recently. Based on these publications, one finds the big picture of the field, which leaves a mixed impression.…”

Section: Introductionmentioning

confidence: 99%

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Fundamentals of flexoelectricity in solids

2013

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The flexoelectric effect is the response of electric polarization to a mechanical strain gradient. It can be viewed as a higher-order effect with respect to piezoelectricity, which is the response of polarization to strain itself. However, at the nanoscale, where large strain gradients are expected, the flexoelectric effect becomes appreciable. Besides, in contrast to the piezoelectric effect, flexoelectricity is allowed by symmetry in any material. Due to these qualities flexoelectricity has attracted growing interest during the past decade. Presently, its role in the physics of dielectrics and semiconductors is widely recognized and the effect is viewed as promising for practical applications. On the other hand, the available theoretical and experimental results are rather contradictory, attesting to a limited understanding in the field. This review paper presents a critical analysis of the current knowledge on the flexoelectricity in common solids, excluding organic materials and liquid crystals.

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Section: Static Bulk Flexoelectric Effect-phenomenologymentioning

confidence: 99%

Section: Internal Bias and Poling Effectmentioning

confidence: 99%

Section: Blocking Boundary Conditionsmentioning

confidence: 99%

Section: Blocking Boundary Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fundamentals of flexoelectricity in solids

2013

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Oxygen Stoichiometry Effect on Polar Properties of LaAlO₃/SrTiO₃

Sharma

Huang

et al. 2018

Adv Funct Materials

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Discovery of a ferroelectric-like behavior of the LaAlO 3 /SrTiO 3 (LAO/STO)interfaces provides an attractive platform for the development of nanoelectronic devices with functionality that can be tuned by electrical or mechanical means. However, further progress in this direction critically depends on deeper understanding of the physicochemical mechanism of this phenomenon. In this report, this problem by testing the electronic properties of the LAO/STO heterostructures with oxygen stoichiometry used as a variable is addressed. Local probe measurements in conjunction with interface electrical characterization allow to establish the field-driven reversible migration of oxygen vacancies as the origin of the ferroelectric-like behavior in LAO/STO. In addition, it is shown that oxygen deficiency gives rise to the formation of micrometer-long atomically sharp boundaries with robust piezoelectricity stemming from a significant strain gradient across the boundary region. These boundaries are not ferroelectric but they can modulate the local electronic characteristics at the interface.The obtained results open a possibility to design and engineer electromechanical functionality in a wide variety of nominally nonpolar and non-piezoelectric complex oxide heterostructures and thin films.to explain its origin with no definitive consensus to date. [2][3][4] Irrespective of the origin, electronic confinement over a 2D plane along with a wide variety of approaches to tune the local electronic density, for example, via epitaxial strain, [5] atomic substitutions, [6] field effect, [7,8] and local charge writing, [9][10][11] offers a viable platform toward realization of advanced nanoelectronic devices. [12][13][14] The recently reported ferroelectric-like behavior of the LAO/STO heterostructures [15][16][17] provides for an alternative tuning mechanism for their electronic properties. The ferroelectric-like [18] behavior in LAO/STO, which manifests itself in an electrically induced switchable polarization, can be used not only to effectively gate the 2DEG at the heterointerface much like in the ferroelectric field effect transistors but also to nondestructively visualize the electrically controlled metal-insulator transitions at the nanoscale. [17,19] In addition, mechanical control of the induced polarization in the LAO/ STO hetero structures presents a new paradigm for voltage-free tuning of 2DEG. [20] Despite these exciting developments, the fundamental mechanism of this phenomenon remains unclear.In one of the earliest attempts to address this problem, it has been established experimentally that the switchable ferroelectric-like behavior of the LAO/STO thin film heterostructures arises from the LAO overlayer. [15] Theoretical

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Second Harmonic Generation Investigation of Symmetry Breaking and Flexoelectricity Induced by Nanoindentations in SrTiO₃

Kolhatkar¹,

Nicklaus²,

Youssef³

et al. 2019

Adv Funct Materials

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Strain gradients induced by nanoindentations in bulk undoped strontium titanate (SrTiO 3 ) are investigated. After indenting a 850 nm deep pattern on the SrTiO 3 surface with a 8 GPa hardness and an 83 GPa indentation modulus by a Berkovich tip, the resulting deformation patterns are imaged by Raman spectroscopy and by second harmonic generation microscopy. Cross-shaped compressively stressed regions along the cubic SrTiO 3 primary slip planes are observed. These zones relax toward the unstrained bulk material through localized strain gradients on a length scale of several microns. Second harmonic tomography reveals the reduction of the crystal's centrosymmetry in the vicinity of the crosslike features due to a strain gradient. These results indicate the appearance of flexoelectricity following the nanoindentation process due to the creation of an inhomogeneous strain.

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Giant flexoelectric effect through interfacial strain relaxation

Cited by 73 publications

References 54 publications

Fundamentals of flexoelectricity in solids

Fundamentals of flexoelectricity in solids

Oxygen Stoichiometry Effect on Polar Properties of LaAlO₃/SrTiO₃

Second Harmonic Generation Investigation of Symmetry Breaking and Flexoelectricity Induced by Nanoindentations in SrTiO₃

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Giant flexoelectric effect through interfacial strain relaxation

Cited by 73 publications

References 54 publications

Fundamentals of flexoelectricity in solids

Fundamentals of flexoelectricity in solids

Oxygen Stoichiometry Effect on Polar Properties of LaAlO3/SrTiO3

Second Harmonic Generation Investigation of Symmetry Breaking and Flexoelectricity Induced by Nanoindentations in SrTiO3

Contact Info

Product

Resources

About

Oxygen Stoichiometry Effect on Polar Properties of LaAlO₃/SrTiO₃

Second Harmonic Generation Investigation of Symmetry Breaking and Flexoelectricity Induced by Nanoindentations in SrTiO₃