Microstructure of PbTiO<sub>3</sub> thin films deposited on (001)MgO by MOCVD

Gao, Yufei; Bai, G. R.; Merkle, K. L.; Shi, Yuxin; Chang, Herng-Hua; Shen, Zhongshan; Lam, D. J.

doi:10.1557/jmr.1993.0145

Cited by 65 publications

(15 citation statements)

References 9 publications

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“…II). For PbTiO 3 and BaTiO 3 films grown on dissimilar cubic substrates, the "misfit strain-temperature" phase diagrams are constructed, which show the stability ranges of various possible polydomain and single-domain states (Sec. III).…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

2001

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A Landau-Ginsburg-Devonshire-type nonlinear phenomenological theory is presented, which enables the thermodynamic description of dense laminar polydomain states in epitaxial ferroelectric thin films. The theory explicitly takes into account the mechanical substrate effect on the polarizations and lattice strains in dissimilar elastic domains (twins). Numerical calculations are performed for PbTiO 3 and BaTiO 3 films grown on (001)-oriented cubic substrates. The "misfit strain-temperature" phase diagrams are developed for these films, showing stability ranges of various possible polydomain and single-domain states. Three types of polarization instabilities are revealed for polydomain epitaxial ferroelectric films, which may lead to the formation of new polydomain states forbidden in bulk crystals. The total dielectric and piezoelectric small-signal responses of polydomain films are calculated, resulting from both the volume and domainwall contributions. For BaTiO 3 films, strong dielectric anomalies are predicted at room temperature near special values of the misfit strain.

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Section: Introductionmentioning

confidence: 99%

“…III). The smallsignal dielectric responses of polydomain PbTiO 3 and BaTiO 3 epitaxial films are calculated numerically, and their changes at the misfit-straindriven structural transformations are discussed (Sec. IV).…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

2001

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“…PACS numbers: 77.80.Dj, 77.22.Ch, 77.55.+f Considerable current interest in ferroelectric thin films is due to their numerous potential applications in electronic devices, which utilize the unique dielectric, pyroelectric, piezoelectric, and electro-optic properties of ferroelectric materials. For many applications, such as dynamic random access memory with very large scale integration, highfrequency transducers, thermistors, and electroluminescent displays, the fabrication of thin films with large electric permittivities is especially important.Recent experimental studies [1][2][3][4][5] have found that, in tetragonal ferroelectric thin films epitaxially grown on cubic substrate, elastic domains (twins) may form during the preparation of heterostructures. The 90 ± domain structure of an epitaxial film has a strong impact on the hysteretic polarization behavior of a ferroelectric layer [4,6].…”

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confidence: 99%

“…Following Kwak et al [1,5], we model this c͞a͞c͞a domain pattern by an infinite periodic array of 90 ± walls. This approximation is justified by the fact that normally 90 ± domain walls in epitaxial films form regular stacks with the in-plane sizes much larger than the domain widths [2,3,5]. Moreover, for thin films it should be especially good because the screening of internal stress fields by the free surface of a film strongly reduces the long-range elastic interactions between 90 ± walls.…”

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confidence: 99%

Prediction of a Giant Dielectric Anomaly in Ultrathin Polydomain Ferroelectric Epitaxial Films

1996

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The amplitudes of electric-field-induced translational vibrations of 90 ± domain walls formed in a tetragonal ferroelectric thin film grown on a cubic substrate are calculated theoretically. The domain wall contribution to the dielectric response of an epitaxial film is evaluated and shown to be important in common heterostructures. In some special film/substrate systems this contribution must increase rapidly with decreasing film thickness, which may result in a giant dielectric anomaly. PACS numbers: 77.80.Dj, 77.22.Ch, 77.55.+f Considerable current interest in ferroelectric thin films is due to their numerous potential applications in electronic devices, which utilize the unique dielectric, pyroelectric, piezoelectric, and electro-optic properties of ferroelectric materials. For many applications, such as dynamic random access memory with very large scale integration, highfrequency transducers, thermistors, and electroluminescent displays, the fabrication of thin films with large electric permittivities is especially important.Recent experimental studies [1][2][3][4][5] have found that, in tetragonal ferroelectric thin films epitaxially grown on cubic substrate, elastic domains (twins) may form during the preparation of heterostructures. The 90 ± domain structure of an epitaxial film has a strong impact on the hysteretic polarization behavior of a ferroelectric layer [4,6]. It may be expected that the formation of 90 ± domain walls in the epitaxial film can also increase markedly its electric permittivity because of the field-induced translational displacements of the walls. Indeed these ferroelastic domain walls, in contrast to the purely ferroelectric 180 ± walls, have a thickness much larger than the unit cell size (about 100 Å in BaTiO 3 [7]) so that the lattice potential barriers hindering their translational motion must be negligible. This supposition is strongly supported by the dielectric measurements on bulk BaTiO 3 single crystals with a laminar 90 ± domain structure [8], which clearly demonstrate that displacements of the 90 ± wall can be induced even by a weak measuring field E ϳ 1 kV͞m. In addition, it has been shown [9-13] that the vibrational motion of 90 ± walls must contribute considerably to the dielectric response of tetragonal ferroelectric ceramics.The above considerations motivated us to perform the first theoretical analysis of the domain wall vibrations in epitaxial ferroelectric thin films. In this Letter, we show that very large permittivities e ϳ 10 5 may arise from these vibrations in the heterostructures involving ultrathin films and pairs of materials having lattice misfits near some special value.Consider a thin tetragonal ferroelectric film epitaxially grown on a cubic substrate with the (001) plane parallel to the surface. Three variants of elastic domains can ex-ist in such a film: c domains with the tetragonal c axis perpendicular to the film surface and a 1 and a 2 domains in which the c axes are parallel to the [100] and [010] axes of the substrate, respectively. In acco...

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“…Polydomain states have been observed in PbTiO 3 , Pb(Zr x Ti 1Ϫx )O 3 , (Pb 1Ϫx La x )TiO 3 , KNbO 3 , and YBa 2 Cu 3 O 7 thin films grown on various substrates. [1][2][3][4][5][6][7][8][9][10][11][12][13] Important data have been obtained showing that the formation of multiple domain patterns may influence significantly the physical properties of ferroelectric films. It was found, for instance, that the relative population of ferroelastic domains in the film has a strong impact on the polarization hysteresis loops exhibited by ferroelectric layers.…”

Section: Introductionmentioning

confidence: 99%

Effect of finite domain-wall width on the domain structures of epitaxial ferroelectric and ferroelastic thin films

Emelyanov

Pertsev

Salje

2001

Journal of Applied Physics

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A theory of domain (twin) structures, which takes into account the finite width of domain walls, is developed for epitaxial ferroelectric and ferroelastic thin films. The theory is based on the dislocation–disclination modeling of the sources of mechanical stresses in polydomain films. Calculations are performed for an orthorhombic or tetragonal film grown on a dissimilar orthorhombic, tetragonal, or cubic substrate. The case of a laminar 90° domain structure with the walls inclined at 45° to the film/substrate interface (c/a/c/a structure in tetragonal films) is considered. A simple dislocation–disclination model is constructed for the junctions of thick domain walls with the film/substrate interface. Using this model, the stress fields in the film and substrate and the associated elastic energy are evaluated. By minimizing the total energy of the material system at a fixed domain-wall width, the equilibrium geometric parameters of a periodic 90° domain structure are calculated. Then the range of stability of this structure in epitaxial films is determined as a function of the wall width. The mechanical restoring forces, which hinder cooperative translational vibrations of thick 90° walls near their equilibrium positions, are also calculated. On this basis, the domain-wall contributions to the dielectric and piezoelectric responses of prepolarized ferroelectric films are evaluated at different wall widths. Finally, the influence of the film straining by the substrate on the equilibrium domain-wall width is analyzed. An increase of the wall width in an epitaxial thin film relative to that in a bulk crystal is predicted.

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Microstructure of PbTiO₃ thin films deposited on (001)MgO by MOCVD

Cited by 65 publications

References 9 publications

Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

Prediction of a Giant Dielectric Anomaly in Ultrathin Polydomain Ferroelectric Epitaxial Films

Effect of finite domain-wall width on the domain structures of epitaxial ferroelectric and ferroelastic thin films

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Microstructure of PbTiO3 thin films deposited on (001)MgO by MOCVD

Cited by 65 publications

References 9 publications

Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

Prediction of a Giant Dielectric Anomaly in Ultrathin Polydomain Ferroelectric Epitaxial Films

Effect of finite domain-wall width on the domain structures of epitaxial ferroelectric and ferroelastic thin films

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Microstructure of PbTiO₃ thin films deposited on (001)MgO by MOCVD