Modern Physics of Ferroelectrics: Essential Background

Rabe, Karin M.; Dawber, Matthew; Lichtensteiger, Céline; Ahn, Charles; Triscone, Jean‐Marc

doi:10.1007/978-3-540-34591-6_1

Cited by 302 publications

(352 citation statements)

References 88 publications

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“…From the shape of the hysteresis, a coercive field of E c ¼ 5 Â 10 5 V m À 1 is extracted, which is an order of magnitude larger than in bulk BTO. Such an increase is typically observed for ferroelectric thin films because of domain pinning and finite depolarization fields 27 . …”

Section: Resultsmentioning

confidence: 78%

A strong electro-optically active lead-free ferroelectric integrated on silicon

et al. 2013

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The development of silicon photonics could greatly benefit from the linear electro-optical properties, absent in bulk silicon, of ferroelectric oxides, as a novel way to seamlessly connect the electrical and optical domain. Of all oxides, barium titanate exhibits one of the largest linear electro-optical coefficients, which has however not yet been explored for thin films on silicon. Here we report on the electro-optical properties of thin barium titanate films epitaxially grown on silicon substrates. We extract a large effective Pockels coefficient of r eff ¼ 148 pm V À 1 , which is five times larger than in the current standard material for electrooptical devices, lithium niobate. We also reveal the tensor nature of the electro-optical properties, as necessary for properly designing future devices, and furthermore unambiguously demonstrate the presence of ferroelectricity. The integration of electro-optical active films on silicon could pave the way towards power-efficient, ultra-compact integrated devices, such as modulators, tuning elements and bistable switches.

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Section: Resultsmentioning

confidence: 78%

A strong electro-optically active lead-free ferroelectric integrated on silicon

et al. 2013

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“…The coexistence of ferroelectricity and antiferroelectricity observed in thin films is attributed to a combination of strain and depolarization field effects. [2,3] in that its structure is obtained through distortion of a nonpolar high-symmetry reference structure; for ferroelectrics the distortion is polar, while for antiferroelectrics it is nonpolar. However, not all nonpolar phases thus obtained are antiferroelectric; in addition, there must be an alternative ferroelectric phase obtained by a polar distortion of the same reference structure, close enough in free energy so that an applied electric field can induce a first-order phase transition from the antiferroelectric to the ferroelectric phase, producing a characteristic polarization-electric field (P-E) double-hysteresis loop.…”

mentioning

confidence: 99%

Antiferroelectricity and ferroelectricity in epitaxially strained PbZrO3from first principles

Reyes‐Lillo

Rabe

2013

Phys. Rev. B

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Density functional calculations are performed to study the effect of epitaxial strain on PbZrO3. We find a remarkably small energy difference between the epitaxially strained polar R3c and nonpolar Pbam structures over the full range of experimentally accessible epitaxial strains -3 % η 4 %. While ferroelectricity is favored for all compressive strains, for tensile strains the small energy difference between the nonpolar ground state and the alternative polar phase yields a robust antiferroelectric ground state. The coexistence of ferroelectricity and antiferroelectricity observed in thin films is attributed to a combination of strain and depolarization field effects. [2,3] in that its structure is obtained through distortion of a nonpolar high-symmetry reference structure; for ferroelectrics the distortion is polar, while for antiferroelectrics it is nonpolar. However, not all nonpolar phases thus obtained are antiferroelectric; in addition, there must be an alternative ferroelectric phase obtained by a polar distortion of the same reference structure, close enough in free energy so that an applied electric field can induce a first-order phase transition from the antiferroelectric to the ferroelectric phase, producing a characteristic polarization-electric field (P-E) double-hysteresis loop. The electric-field-induced transition is the source of functional properties and promising technological applications. Non-linear strain and dielectric responses at the phase switching are useful for transducers and electrooptic applications [4,5]. The shape of the double hysteresis loop suggests applications in high-energy storage capacitors [6,7]. In addition, an effective electro-caloric effect can also be induced in systems with a large entropy change between the two phases [8].Lead zirconate PbZrO 3 (PZO) was the first material identified as antiferroelectric [9]. Despite extensive studies and characterization, PZO continues to offer insights into the origin and complexity of antiferroelectricity [10,11]. In bulk form, PZO has a cubic perovskite structure at high temperatures and a nonpolar orthorhombic ground state below T c ∼ 505 K. The ground state has space group Pbam [12, 13] and unit cell dimensions √ 2a 0 × 2 √ 2a 0 × 2a 0 with respect to the reference lattice constant a 0 . Its distorted perovskite structure is derived from the cubic (C) unit cell through a nonpolar Σ 2 distortion mode of Pb +2 ion displacements in the 110 C direction, combined with oxygen octahedron rotation R − 5 modes around the 110 C axis (a − a − c 0 in Glazer notation). Under an applied electric field, PZO single crystals undergo a first order phase transition into a sequence of polar phases with rhombohedral symmetry [14]. Similar rhombohedral polar phases are observed in the polycrystalline ceramic system Pb(Zr 1−x Ti x )O 3 under small 5-10 % isovalent substitution of zirconium for titanium [15,16]. In thin films, the competition between the rhombohedral low-energy structures and the PZO ground state is less studied. Room temperature ...

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“…In the molecular liquid crystal community, this tendency has been thought to decrease the number of defects in columnar phases, which is important if these columnar phases are to replace 8 the crystalline ferroelectrics (materials with a permanent electric polarization) in (future) applications, such as sensors, electromechanical devices, and nonvolatile memory. 9 Several bowl-shaped molecules have already been synthesized and found to form columnar phases. 10 In addition, buckybowlic molecules, that is, fragments of C 60 whose dangling bonds have been saturated with hydrogen atoms, have been shown to crystallize in a columnar fashion.…”

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Phase Behavior and Structure of a New Colloidal Model System of Bowl-Shaped Particles

et al. 2010

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We study the phase behavior of bowl-shaped (nano)particles using confocal microscopy and computer simulations. Experimentally, we find the formation of a wormlike fluid phase in which the bowl-shaped particles have a strong tendency to stack on top of each other. However, using free energy calculations in computer simulations, we show that the wormlike phase is out-ofequilibrium and that the columnar phase is thermodynamically stable for sufficiently deep bowls and high densities. In addition, we employ a novel technique based on simulated annealing to predict the crystal structures for shallow bowls. We find four exotic new crystal structures and we determine their region of stability using free energy calculations. We discuss the implications of our results for the development of materials consisting of molecular mesogens or nanoparticles.KEYWORDS Nanobowls, crystal structures, computer simulations, phase diagram, columnar liquid crystals I n recent years, a whole variety of bowl-shaped nanoparticles and colloids have been synthesized and characterized, 1-6 and possible applications of these systems have been put forward. Most of these applications are of a single particle nature, such as a nanocontainer, 4 or for metallic nanobowls depend on the tendency of these particles to form foamlike structures upon aggregation. Applications of the latter kind include superhydrophobic 5 and infrared-blocking 3 coatings. Metallic nanoparticles can be stabilized, for example, by applying a capping layer, 7 which should prevent aggregation and thus reveal the natural tendency of bowl-shaped particles to form stacks or columns. In the molecular liquid crystal community, this tendency has been thought to decrease the number of defects in columnar phases, which is important if these columnar phases are to replace 8 the crystalline ferroelectrics (materials with a permanent electric polarization) in (future) applications, such as sensors, electromechanical devices, and nonvolatile memory. 9 Several bowl-shaped molecules have already been synthesized and found to form columnar phases. 10 In addition, buckybowlic molecules, that is, fragments of C 60 whose dangling bonds have been saturated with hydrogen atoms, have been shown to crystallize in a columnar fashion. 11-15 An aligned phase of metallic nanobowls could also be a promising novel material, since the individual particles have strongly anisotropic optical properties. 1,3 However, no systematic experimental studies of the structure of nanobowls in solution exist to our knowledge, and therefore it remains an open question whether or not bowlshaped nanoparticles and colloids can form stacks and ordered structures. This issue is also not easily resolved using theory or simulations as it is difficult to model the complicated particle shape, although a recent simulation study 8 exists in which the attractive-repulsive Gay-Berne potential was generalized to a bowl-shaped particle. In another very recent simulation study 16 of hard contact lenses (infinitely thin, shall...

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Modern Physics of Ferroelectrics: Essential Background

Cited by 302 publications

References 88 publications

A strong electro-optically active lead-free ferroelectric integrated on silicon

A strong electro-optically active lead-free ferroelectric integrated on silicon

Antiferroelectricity and ferroelectricity in epitaxially strained PbZrO3from first principles

Phase Behavior and Structure of a New Colloidal Model System of Bowl-Shaped Particles

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