Formation of artificial BaTiO3/SrTiO3 superlattices using pulsed laser deposition and their dielectric properties

Tabata, Hitoshi; Tanaka, Hidekazu; Kawai, Tomoji

doi:10.1063/1.112837

Cited by 435 publications

(246 citation statements)

References 16 publications

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confidence: 99%

“…[1][2][3][4][5][6][7] For example, enhanced FE and dielectric properties could be achieved in SLs composed of FE BaTiO 3 (BTO) and paraelectric (PE) SrTiO 3 (STO) layers. 1,2,6,8 Such enhancement of ferroelectric polarization is known to originate from the strong strain coupling of ferroelectric polarization in BaTiO 3 -based ferroelectrics. 9,10 Recently, by including PE CaTiO 3 (CTO) layers, three-component SLs have been designed and raised an intriguing issue of artificially broken compositional inversion symmetry, 11,12 resulting enhanced ferroelectric properties.…”

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Strain-coupled ferroelectric polarization in BaTiO3–CaTiO3 superlattices

Seo

Lee

2009

Applied Physics Letters

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We report on growth and ferroelectric (FE) properties of superlattices (SLs) composed of the FE BaTiO 3 and the paraelectric (PE) CaTiO 3 . Previous theories have predicted that the polarization in (BaTiO 3 )n/(CaTiO 3 )n SLs increases as the sublayer thickness (n) increases when the same strain state is maintained. However, our BaTiO 3 /CaTiO 3 SLs show a varying lattice-strain state and systematic reduction in polarization with increasing n while coherently-strained SLs with n=1, 2 show a FE polarization of ca. 8.5 µC/cm 2 . We suggest that the strain coupling plays more important role in FE properties than the electrostatic interlayer coupling based on constant dielectric permittivities. *

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confidence: 99%

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confidence: 99%

Strain-coupled ferroelectric polarization in BaTiO3–CaTiO3 superlattices

Seo

Lee

2009

Applied Physics Letters

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“…In ideal superlattices with perfectly flat, compositionally abrupt interfaces, first-principles calculations and experimental studies have shown how factors such as strain due to lattice mismatches 1,2,3,4,5,6,7,8,9,10,11,12,13,14 , charge compensation 15,16,17,18 and bonding at the interface 19 can be controlled to enhance the ferroelectric properties of the superlattice. Work by Dawber and coworkers show that the behavior of very short period superlattices may deviate from that extrapolated from longer periods 11 .…”

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Polarization enhancement in short period superlattices via interfacial intermixing

2007

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The effect of intermixing at the interface of short period PbTiO3/SrTiO3 superlattices is studied using firstprinciples density functional theory. The results indicate that interfacial intermixing significantly enhances the polarization within the superlattice. This enhancement is directly related to the off-centering of Pb and Sr cations and can be explained through a discussion of interacting dipoles. This picture should be general for a wide range of multicomponent superlattices and may have important consequences for the design of ferroelectric devices.Ferroelectric superlattices are a promising paradigm for creating novel materials for device applications. In ideal superlattices with perfectly flat, compositionally abrupt interfaces, first-principles calculations and experimental studies have shown how factors such as strain due to lattice mismatches 1,2,3,4,5,6,7,8,9,10,11,12,13,14 , charge compensation 15,16,17,18 and bonding at the interface 19 can be controlled to enhance the ferroelectric properties of the superlattice. Work by Dawber and coworkers show that the behavior of very short period superlattices may deviate from that extrapolated from longer periods 11 . While, these effects may be the result of a number of different factors, it seems likely that changes at the interface dominate at these length scales. Recent high resolution CO-BRA studies on SrTiO 3 (STO) supported PbTiO 3 (PTO) thin films further suggest that cation intermixing may be present at the interface of such superlattices 20 .Knowledge of how interfacial cation intermixing influences the aggregate properties of a superlattice can be useful in tuning its properties. As the superlattice period decreases, these effects become more important and, depending on their strength, may dominate. In this paper, we present a first principles study on the effect of interfacial cation intermixing on the polarization of short period PTO/STO superlattices. Our results demonstrate that intermixing significantly enhances the polarization and that this enhancement is directly linked to larger Pb displacements in the intermixed layers. We use density functional theory (DFT) to examine the effects of interlayer cation mixing on the polarization within PTO/STO superlattices. We compare superlattices with sharp interfaces with three different compositionally equivalent intermixed systems of m=1-3 PTO layers and n=1-3 STO layers (figure 1). Checkered, striped and 25%/75% intermixed layers were studied. Intermixed layers were placed at each of the mixed PTO/STO interfaces; giving a total composition of 50% PTO / 50% STO. The two intermixed layers account for one PTO and one STO layer. All calculations were performed using projector augmented wave (PAW) potentials 22,23 with the Vienna Ab initio Simulation Package (VASP v4.6.26) 21 , with the local density approximation for the exchange correlation functional. A 600 eV (22 Ha) cutoff and a 4×4×4 k point mesh were used. STO was found to be cubic with a lattice constant of 3.863Å (experiment: 3.905Å 24 ). T...

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“…Some research groups have succeeded in fabricating perovskite type artificial superlattices [1 -5]. An anomaly of dielectric properties in BaTiO 3 /SrTiO 3 (BTO/STO) superlattice was pointed out by Tabata et al [3] and Nam et al [4]. However, the dielectric properties of BTO/STO superlattices are still not very reliable because superlattices made in an ultra-high vacuum system usually show high-leakage currents.…”

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confidence: 99%

Anomalous dielectric and optical properties in perovskite-type artificial superlattices

Tsurumi

Harigai

Tanaka

et al. 2004

Science and Technology of Advanced Materials

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Perovskite-type BaTiO 3 /SrTiO 3 (BTO/STO) artificial superlattices were fabricated by molecular beam epitaxy process and their dielectric properties and refractive indices were measured. A large leakage current was observed in the films on Nb-doped STO substrate. Dielectric permittivity was therefore measured using planer interdigital electrodes. Fine planer electrodes were necessary to reduce the penetration of electric flux into the substrate. Interdigital electrodes were formed by electron-beam lithography. Dielectric permittivity of superlattices along the film surface was determined using electromagnetic field analysis. It was found that the dielectric permittivity of the BTO/STO superlattice with the period of 10 unit cells showed a maximum value above 30,000, which was almost independent from frequency up to 110 MHz. The refractive index of superlattices measured with a spectroscopic ellipsometer also showed the highest value when the period was 10 unit cells. This indicated that the structure of superlattices affected not only the ionic polarization but also the electric polarization. The origin of anomalous properties observed in superlattices may be interpreted by the strains induced into the film. q

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Formation of artificial BaTiO3/SrTiO3 superlattices using pulsed laser deposition and their dielectric properties

Cited by 435 publications

References 16 publications

Strain-coupled ferroelectric polarization in BaTiO3–CaTiO3 superlattices

Strain-coupled ferroelectric polarization in BaTiO3–CaTiO3 superlattices

Polarization enhancement in short period superlattices via interfacial intermixing

Anomalous dielectric and optical properties in perovskite-type artificial superlattices

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