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26 Mar 2007

Volume 90, Issue 13, Articles (13xxxx)

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Appl. Phys. Lett. 90, 134101 (2007); http://dx.doi.org/10.1063/1.2679209 (3 pages)

S. Srinivasan, J. Hiller, B. Kabius, and O. Auciello
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Electric energy density of dielectric nanocomposites

J. Y. Li, L. Zhang, and Stephen Ducharme

Appl. Phys. Lett. 90, 132901 (2007); http://dx.doi.org/10.1063/1.2716847 (3 pages) | Cited 41 times

Online Publication Date: 26 March 2007

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Dielectric materials with large electric energy density are actively pursued for many applications. The authors analyze the effective permittivity, breakdown strength, and electric energy density of dielectric nanocomposites using an effective medium approximation, modeling the nanocomposite as a three-phase material by the double-inclusion method. The addition of nanoparticles enhances the permittivity but reduces the breakdown strength, making the potential gain in electric energy density small. In addition, the interfacial interaction shifts the “percolation” threshold toward lower volume fraction of nanoparticles. The analysis suggests that the microstructure of nanocomposites must be carefully controlled to maintain high dielectric strength and therefore realize enhanced electric energy density.
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77.84.Lf Composite materials
77.22.Jp Dielectric breakdown and space-charge effects
77.22.Ch Permittivity (dielectric function)

Thickness dependence of in-plane dielectric and ferroelectric properties of Ba0.7Sr0.3TiO3 thin films epitaxially grown on LaAlO3

X. Y. Zhou, D. Y. Wang, R. K. Zheng, H. Y. Tian, J. Q. Qi, H. L. W. Chan, C. L. Choy, and Y. Wang

Appl. Phys. Lett. 90, 132902 (2007); http://dx.doi.org/10.1063/1.2716865 (3 pages) | Cited 4 times

Online Publication Date: 26 March 2007

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The authors have studied the effects of film thickness on the lattice strain and in-plane dielectric and ferroelectric properties of Ba0.7Sr0.3TiO3 thin films epitaxially grown on LaAlO3 (001) single crystal substrates. With increasing film thickness from 20 to 300 nm, the in-plane lattice parameter (a) increased from 0.395 to 0.402 nm while the out-of-plane lattice parameter (c) remained almost unchanged, which led to an increased a/c ratio (tetragonality) changing from 0.998 to 1.012 and consequently resulted in a shift of Curie temperature from 306 to 360 K associated with an increase of the in-plane remnant polarization and dielectric constant of the film.
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77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Band gap and Schottky barrier heights of multiferroic BiFeO3

S. J. Clark and J. Robertson

Appl. Phys. Lett. 90, 132903 (2007); http://dx.doi.org/10.1063/1.2716868 (3 pages) | Cited 77 times

Online Publication Date: 26 March 2007

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BiFeO3 is an interesting multiferroic oxide and a potentially important Pb-free ferroelectric. However, its applications can be limited by large leakage currents. Its band gap is calculated by the density-functional based screened exchange method to be 2.8 eV, similar to experiment. The Schottky barrier height on Pt or SrRuO3 is calculated in the metal induced gap state model to be over 0.9 eV. Thus, its leakage is not intrinsic.
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71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
73.30.+y Surface double layers, Schottky barriers, and work functions
75.80.+q Magnetomechanical effects, magnetostriction
77.80.-e Ferroelectricity and antiferroelectricity
75.50.Dd Nonmetallic ferromagnetic materials

Critical temperatures of 70%Pb(Mg1/3Nb2/3)O3–30%PbTiO3 thin films investigated by dielectric, ferroelectric, and structural measurements

X. J. Meng, D. Rémiens, M. Detalle, B. Dkhil, J. L. Sun, and J. H. Chu

Appl. Phys. Lett. 90, 132904 (2007); http://dx.doi.org/10.1063/1.2716312 (3 pages) | Cited 3 times

Online Publication Date: 27 March 2007

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The authors have investigated the temperature dependence of the ferroelectric, dielectric, and structural properties of 70%Pb(Mg1/3Nb2/3)O3–30%PbTiO3 thin films. Two critical temperatures were evidenced. The first one occurring around 410 K corresponds to the bulk paraelectric-ferroelectric phase transition and the second one around 200 K is rather related to a self-arrangement of small domains into macrodomains in order to minimize elastic energies. A multiscale domainlike structure is induced and the temperature evolution of such complex structure can be revealed through pronounced changes occurring in the nonlinear dielectric susceptibility.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
68.55.-a Thin film structure and morphology
42.65.An Optical susceptibility, hyperpolarizability

(1−x)BaTiO3−x(Na0.5K0.5)NbO3 ceramics for multilayer ceramic capacitors

Chang-Hak Choi, Cheol-Woo Ahn, Sahn Nahm, Jung-Oh Hong, and Jung-Soo Lee

Appl. Phys. Lett. 90, 132905 (2007); http://dx.doi.org/10.1063/1.2717559 (3 pages) | Cited 13 times

Online Publication Date: 28 March 2007

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(1−x)BaTiO3−x(Na0.5K0.5)NbO3 ceramics with 0.0 ⩽ x ⩽ 0.08 formed a homogeneous solid solution. As (Na0.5K0.5)NbO3 (NKN) was added, the Curie temperature of the BaTiO3 (BT) ceramics decreased and specimens became a relaxor as x exceeded 0.04. The grain size of the BT ceramics decreased with increasing NKN. The average grain size was approximately 0.4 μm at x = 0.06. The dielectric constant (εr) of the specimen increased with increasing NKN and high εr of 7402 with low dielectric loss of <1.0% was observed for the 0.94BT-0.06NKN ceramic. Therefore, the 0.94BT-0.06NKN ceramic is proposed as a promising candidate material for thin multilayer ceramic capacitors with high capacitance.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
84.32.Tt Capacitors

Thickness effects on the electrical characteristics of Ba0.7Sr0.3TiO3 capacitors with nano-Cr interlayer

Chia-Cheng Ho, Bi-Shiou Chiou, and Li-Chun Chang

Appl. Phys. Lett. 90, 132906 (2007); http://dx.doi.org/10.1063/1.2717553 (3 pages) | Cited 3 times

Online Publication Date: 29 March 2007

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A multilayer Ba0.7Sr0.3TiO3/Cr/Ba0.7Sr0.3TiO3 (BST/Cr/BST) structure was sputtered sequentially onto Pt/Ti/SiO2/Si substrate. With the insertion of a 2 nm Cr interlayer, the temperature coefficient of capacitance of the BST/Cr/BST dielectric is about 69% lower than that of BST monolayer dielectric. The dielectric constant and dissipation factor as the function of Cr thickness are studied. X-ray diffraction patterns, the analysis results of energy dispersive spectroscopy, and the survey scan profiles of Auger electron spectroscopy reveal the formation of a TiO2 secondary phase after the multilayer is annealed at 800 °C in O2 atmosphere. The insertion of nano-Cr interlayer improves the electrical properties of BST capacitors.
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84.32.Tt Capacitors

Ferrite with extraordinary electric and dielectric properties prepared from self-combustion technique

Qian Chen, Piyi Du, Wenyan Huang, Lu Jin, Wenjian Weng, and Gaorong Han

Appl. Phys. Lett. 90, 132907 (2007); http://dx.doi.org/10.1063/1.2718482 (3 pages) | Cited 8 times

Online Publication Date: 30 March 2007

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Nickel-zinc ferrites (Ni0.5Zn0.5Fe2O4) with extraordinary electric and dielectric properties were prepared by self-combustion technique. The resistivity of ferrite in the ferric citrate system is on the order of 1010 Ω cm, which is about four orders higher than that of ferrite in the ferric nitrate system as well as that of ferrite prepared by the conventional method. The dielectric loss of sample in the ferric citrate system is only 0.008. The amorphous phase and its encapsulation well around the grains have played most important roles in both high resistivity and low dielectric loss of ferrite in the ferric citrate system.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.22.Gm Dielectric loss and relaxation
72.80.Sk Insulators
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Gg Ferrimagnetics
75.50.Tt Fine-particle systems; nanocrystalline materials

Precise control of phase transformation process in lead zirconate titanate thin films by focused line-beam scanning

Jang-Sik Lee, Jung-Kun Lee, and Seung-Ki Joo

Appl. Phys. Lett. 90, 132908 (2007); http://dx.doi.org/10.1063/1.2719636 (3 pages)

Online Publication Date: 30 March 2007

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Phase transformation and grain growth processes of lead zirconate titanate (PZT) thin films have been precisely controlled by using focused line-beam scanning. The authors promoted the lateral crystallization of PZT grains by controlling a nucleation process and increasing the size of single grains to be as large as 40 μm in length. Focused line-beam scanning allows for the selective growth and crystallization of large PZT grains on predetermined nucleation sites. The high growth rate of the selected PZT grains was attributed to successive suppression of undesirable nucleation except at predetermined positions when pretreated PZT films were exposed to the focused line beam.
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64.70.K- Solid-solid transitions
64.60.Q- Nucleation
77.55.-g Dielectric thin films
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