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24 Sep 2001

Volume 79, Issue 13, pp. 1933-2115

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Impact of domain wall displacements on the dielectric permittivity of epitaxial Ba0.5Sr0.5TiO3 films

Yu. A. Boikov and T. Claeson

Appl. Phys. Lett. 79, 2052 (2001); http://dx.doi.org/10.1063/1.1405147 (3 pages) | Cited 6 times

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Contributions of ferroelectric domain wall oscillations to the loss factor, tan δ, and the real part of the dielectric permittivity, ε′, of 700 nm thick Ba0.5Sr0.5TiO3 layers were considered. The domain wall related relaxation in the ferroelectric layer exhibited thermally activated behavior with a hindering barrier φ ≈ 0.08 eV. The tan δ(T) of the layer peaked and there was a hump anomaly in ε′(T) at a temperature where the relaxation rate matched the frequency of measurement. © 2001 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
77.22.Gm Dielectric loss and relaxation

Direct effect of illumination on ferroelectric properties of lead zirconate titanate thin films

A. L. Kholkin, S. O. Iakovlev, and J. L. Baptista

Appl. Phys. Lett. 79, 2055 (2001); http://dx.doi.org/10.1063/1.1402639 (3 pages) | Cited 7 times

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Photosensitive ferroelectric materials exhibit various photoferroelectric phenomena due to the strong influence of nonequilibrium charge carriers on polarization and phase transition. These phenomena are essential for a number of applications including photodriven actuators and sensitive photodetectors. In this work, the effect of UV illumination on dielectric and piezoelectric properties is investigated in lead zirconate titanate (PZT) thin films, which are currently the most promising material for microactuator applications. The effective piezoelectric coefficient (d33) and dielectric permittivity (ϵ) of PZT films are simultaneously measured under a weak ac electric field during illumination with a band gap light (λ = 280–400 nm). It is shown that both d33 and ϵ decrease under UV illumination. The reduction of permittivity, however, is much smaller than that of d33 and demonstrates a much slower time relaxation. The d33 decrease is attributed to the reduction of average remanent polarization under the UV light. Thus a direct effect of the photoactive light on ferroelectric polarization is observed under essentially nondestructive (weak-field) conditions. The origin of the observed effect is discussed along with the possible implications for thin-film devices. © 2001 American Institute of Physics.
Show PACS
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
72.40.+w Photoconduction and photovoltaic effects
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
77.65.Bn Piezoelectric and electrostrictive constants

Nanopolar reorientation in ferroelectric thin films

C. Hubert, J. Levy, T. V. Rivkin, C. Carlson, P. A. Parilla, J. D. Perkins, and D. S. Ginley

Appl. Phys. Lett. 79, 2058 (2001); http://dx.doi.org/10.1063/1.1406146 (3 pages) | Cited 13 times

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The influence of varying oxygen pressure P(O2) during the growth of Ba0.4Sr0.6TiO3 thin films is investigated using dielectric and local optical probes. A transition from in-plane to out-of-plane ferroelectricity is observed with increasing P(O2). Signatures of in-plane and out-of-plane ferroelectricity are identified using dielectric response and time-resolved confocal scanning optical microscopy (TRCSOM). At the crossover pressure between in-plane and out-of-plane polarization (Pc = 85 mTorr), TRCSOM measurements reveal a soft, highly dispersive out-of-plane polarization that reorients in plane under modest applied electric fields. At higher deposition pressures, the out-of-plane polarization is hardened and is less dispersive at microwave frequencies, and the dielectric tuning is suppressed. Nanopolar reorientation is believed to be responsible for the marked increase in dielectric tuning at P(O2) = Pc. © 2001 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films

Significant dielectric enhancement in 0.3BiFeO3–0.7SrBi2Nb2O9

Haoshuang Gu, Junmin Xue, and John Wang

Appl. Phys. Lett. 79, 2061 (2001); http://dx.doi.org/10.1063/1.1405420 (3 pages) | Cited 15 times

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Significant dielectric enhancement is observed in 0.3BiFeO3–0.7SrBi2Nb2O9, when a single-phase layered perovskite structure was formed by sintering the mechanically activated oxide composition. The Curie point of xBiFeO3–(1−x)SrBi2Nb2O9 was shifted upward with an increase in the BiFeO3 content. 0.3BiFeO3–0.7SrBi2Nb2O9 exhibits a dielectric constant of 1.84×105 at the Curie point of 750 °C. The lattice dimensions of xBiFeO3–(1−x)SrBi2Nb2O9 decrease slightly with an increase in the content of BiFeO3 over the composition range of x=0–0.2, while 0.3 mol BiFeO3 in SrBi2Nb2O9 led to recovery in the lattice dimensions. The much enhanced dielectric properties observed in 0.3BiFeO3–0.7SrBi2Nb2O9 are therefore due to the enlarged rattling space for both Nb5+ and in particular for smaller Fe3+. © 2001 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.66.Fn Inorganic compounds
77.22.Ch Permittivity (dielectric function)

Impurities in dielectrics and hydrogen barriers for SrBi2Ta2O9-based ferroelectric memories

B. Yang, S. H. Oh, C. H. Chung, K. H. Noh, Y. M. Kang, S. S. Lee, S. K. Hong, N. S. Kang, and J. H. Hong

Appl. Phys. Lett. 79, 2064 (2001); http://dx.doi.org/10.1063/1.1403664 (3 pages) | Cited 3 times

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We report results of systematic investigation of impurities in dielectrics and hydrogen barriers (Ti and Al2O3 films) during the integration process of SrBi2Ta2O9-based ferroelectric memories. The capacitors integrated with Ti hydrogen barriers are not electrically degraded regardless of the annealing conditions of the subdielectrics. On the contrary, electrical properties of the capacitors using Al2O3 hydrogen barriers significantly depend on the annealing temperatures for subdielectrics. It turned out that interaction of the dielectrics with plasma during sputtering of the Ti films caused fragmentation of the moisture in the dielectrics and absorption of the hydrogen in the Ti films, making annealing irrelevant. However, the alumina films blocked both hydrogen and moisture in the subdielectrics during the passivation process, resulting in dependence on the annealing temperatures. © 2001 American Institute of Physics.
Show PACS
85.50.Gk Non-volatile ferroelectric memories
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
81.15.Cd Deposition by sputtering
77.80.Dj Domain structure; hysteresis

Low leakage current and good ferroelectric properties of SrBi2(Ta0.7Nb0.3)2O9–Bi3TiTaO9 solid solution thin film

Masatoshi Mitsuya, Norimasa Nukaga, Takayuki Watanabe, Hiroshi Funakubo, Keisuke Saito, and Minoru Osada

Appl. Phys. Lett. 79, 2067 (2001); http://dx.doi.org/10.1063/1.1407858 (3 pages) | Cited 5 times

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(1−x)SrBi2(Ta0.7Nb0.3)2O9+xBi3TiTaO9 (x = 0–0.5) solid-solution (SBTN+BTT) films of low defect contents were directly crystallized on (111)Pt/Ti/SiO2/Si substrates at 650 °C by metalorganic chemical vapor deposition. The deposited films showed a strong (103) orientation. The remanent polarization (Pr) of the directly crystallized SBTN (x = 0) was very small. However, the Pr value increased to 7.1 μC/cm2 by adding 30% of BTT (x = 0.3) and was almost equal to that of Sr0.8Bi2.2(Ta0.7Nb0.3)2O9(S0.8B2.2TN), which is widely studied for nonvolatile memory applications. The leakage current density of the SBTN+BTT solid solution was on the order of 10−8 A/cm2 for fields up to 200 kV/cm due to its low defect contents character, while that of S0.8B2.2TN was above 10−6 A/cm2 due to the existence of defects in the Sr sites. The solid-solution film showed a fatigue-free character. © 2001 American Institute of Physics.
Show PACS
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.22.Ej Polarization and depolarization
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