Dimension and Size Effects in Ferroelectrics

Li, Shaoping; Eastman, J. A.; Vetrone, J.; Foster, C. M.; Newnham, R. E.

doi:10.1143/jjap.36.5169

Cited by 106 publications

(62 citation statements)

References 35 publications

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“…These include the intrinsic size effect on ferroelectricity, [14][15][16] the influence of depolarizing field, 17,18 the surface tension effect, 8 and the surface bond contraction. 19 In ceramic materials, where individual crystallites are surrounded by a ferroelectric medium, the mechanical effect caused by the elastic three-dimensional ͑3D͒ clamping of crystallites may play an important role.…”

Section: Introductionmentioning

confidence: 99%

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Zembilgotov

Pertsev

Waser

2005

Journal of Applied Physics

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Using a nonlinear thermodynamic theory, we describe equilibrium polarization states and the macroscopic dielectric response of nanocrystalline ferroelectric ceramics with single-domain grains. The elastic clamping of individual crystallites by the surrounding material is explicitly taken into account via the introduction of a specific thermodynamic potential. Aggregate material properties are calculated with the aid of an iterative procedure based on the method of effective medium. The numerical calculations, performed for unpolarized BaTiO3 and Pb(Zr1−xTix)O3 ceramics, demonstrate that the equilibrium phase states of nanocrystalline ceramics may differ drastically from those of single crystals and coarse-grained materials. Remarkably, the theory predicts the coexistence of rhombohedral and tetragonal crystallites in nanocrystalline Pb(Zr1−xTix)O3 ceramics in a wide range of compositions and temperatures. For BaTiO3 ceramics, a mixture of rhombohedral and orthorhombic crystallites is found to be the energetically most favorable state at room temperature. The calculations also show that the dielectric properties of nanocrystalline ferroelectric ceramics may be very different from those of conventional materials due to the elastic clamping of single-domain crystallites.

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Section: Introductionmentioning

confidence: 99%

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Zembilgotov

Pertsev

Waser

2005

Journal of Applied Physics

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“…Unfortunately a thickness reduction from the macroscopic down to the mesoscopic regimes results in a change of polarization stability, although the polarization itself can be either inhibited or enhanced. [1][2][3][4][5][6] As the structural and polarization properties of these ultra thin films cannot readily be obtained by conventional techniques, there is a need for novel and reliable characterization techniques.…”

Section: Introductionmentioning

confidence: 99%

Domain orientation in ultrathin (Ba,Sr)TiO3 films measured by optical second harmonic generation

Мишина

Sherstyuk

Barskiy

et al. 2003

Journal of Applied Physics

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The analysis of polarization diagrams for specular and scattered second harmonic generation ͑SHG͒ was used for the structural characterization of submicron domain structures of thin (Ba,Sr͒TiO 3 ͑BST͒ films. It is shown that the lack of separation of these two contributions may lead to completely wrong conclusions about the domain orientation in these films. SHG studies of the thickness dependence of domain fractions ͑including 180°domains͒ reveal the presence of ferroelectric domains in ultrathin BST films ͑6 nm͒, although no domain structure was observed by atomic force microscopy. Thus the presence of ferroelectric ordering was demonstrated in perovskite films with a thickness down to 6 nm.

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“…3 we show the normalized polarization (termed as the order parameter) as a function of film thickness normalized to the correlation length, ͑d / ͒. The value of for this particular composition was calculated to be 2.4 nm using parameters from Li 20 and Zembilgotov. 10 We also plot the predicted thickness dependence, from an intrinsic size effect model 9,10,20 (solid plot), from the macroscopic depoling field model 14,15 (dashed plot), and ab initio calculations for SRO/ BaTiO 3 / SRO (dotted plot).…”

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Size effects in ultrathin epitaxial ferroelectric heterostructures

Valanoor

Prasertchoung

Zhao

et al. 2004

Applied Physics Letters

114

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In this letter we report on the effect of thickness scaling in model PbZr 0.2 Ti 0.8 O 3 ͑PZT͒ / SrRuO 3 heterostructures. Although theoretical models for thickness scaling have been widely reported, direct quantitative experimental data for ultrathin perovskite ͑Ͻ10 nm͒ films in the presence of real electrodes have still not been reported. In this letter we show a systematic quantitative experimental study of the thickness dependence of switched polarization in (001) epitaxial PZT films, 4 to 80 nm thick. A preliminary model based on a modified Landau Ginzburg approach suggests that the nature of the electrostatics at the ferroelectric-electrode interface plays a significant role in the scaling of ferroelectric thin films. The effect of thickness scaling in ferroelectrics has recently been of immense interest. [1][2][3][4][5][6][7][8][9][10][11][12] As the dimensions (both lateral and vertical direction) of the perovskite layer decreases, the fundamental question of size dependence becomes crucial. From a theoretical point of view, two models have been traditionally used to describe size effects, namely an "intrinsic" effect 9,10,13 and a "depoling field" effect. 4,5,14,15 Experimentally Tybell et al. 8 qualitatively showed that even a 4-nm-thick epitaxial PbZr 0.2 Ti 0.8 O 3 (PZT) film on Nb:STO is ferroelectric. However a direct experimental quantification of the ferroelectric polarization, particularly for films in the sub-10 nm thickness range has not been reported. For such ultrathin films direct experimental quantification of size effects are complicated by extrinsic effects such as leakage and therefore methods other than the traditional P -E hysteresis loop have been reported to characterize the stability of the polar state. 1,7 This letter presents experimental measurements of the switched polarization in PZT films of thickness down to 4 nm, in the presence of real electrodes.A 70-nm-thick SRO layer was grown on STO at 650°C followed by the PZT layer via pulsed laser deposition. The deposition was carried out at 100 mTorr of oxygen and the sample was cooled down from growth temperature 1 atm of oxygen. In order to avoid complications from 90°domain formation the PZT films were grown in a thickness range from 4 to 80 nm, for which they are entirely c-axis oriented. The switchable polarization was measured using a Radiant Technologies Precision Premier system at 16 kHz (hysteresis loops) and an AFM based pulsed probing technique with conductive Pt-Ir tips was employed to measure the pulsed polarization. 16 We focused on the PZT ͑0/20/80͒ composition, since it has an in-plane lattice parameter of 3.94 Å, 17 which is closely lattice matched to SRO͑3.93 Å͒. Figure 1(a) is a low magnification TEM image of a 4 nm (nominal) thick film; the interfaces between SRO and PZT are sharp, identified as dashed lines in the high resolution image, Fig. 1(b). The electrode-ferroelectric interface shows a significantly reduced dislocation density, attributed to the small lattice mismatch (0.7%) at growth temperature of 600...

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Dimension and Size Effects in Ferroelectrics

Cited by 106 publications

References 35 publications

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Phase states of nanocrystalline ferroelectric ceramics and their dielectric properties

Domain orientation in ultrathin (Ba,Sr)TiO3 films measured by optical second harmonic generation

Size effects in ultrathin epitaxial ferroelectric heterostructures

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