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15 Oct 2007

Volume 91, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 91, 162101 (2007); http://dx.doi.org/10.1063/1.2794995 (3 pages)

D. J. Reilly, C. M. Marcus, M. P. Hanson, and A. C. Gossard
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Slow relaxation of piezoelectric response in CdZnTe ferroelectric semiconductor single crystals

Shanming Ke, Haitao Huang, Tao Wang, Huiqing Fan, Waiqi Jie, and H. L. W. Chan

Appl. Phys. Lett. 91, 162901 (2007); http://dx.doi.org/10.1063/1.2799259 (3 pages) | Cited 1 time

Online Publication Date: 15 October 2007

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The piezoelectric response in Cd0.9Zn0.1Te (CZT) semiconductor single crystals has been investigated by analyzing room temperature impedance spectra. The polarization is significantly influenced by light illumination. A slow relaxation process of the piezoelectric response has been observed with a relaxation time of 37 s, which is comparable to the discharge current results. The frequencies for piezoelectric resonance and antiresonance can be tuned to lower values when a bias field is applied and can be recovered when the bias field is removed. These phenomena may be universal for ferroelectric semiconductors and can be explained by a slow relaxation model in dielectrics.
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77.22.Gm Dielectric loss and relaxation
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
77.65.Fs Electromechanical resonance; quartz resonators

Dielectric properties of dysprosium- and scandium-doped hafnium dioxide thin films

C. Adelmann, V. Sriramkumar, S. Van Elshocht, P. Lehnen, T. Conard, and S. De Gendt

Appl. Phys. Lett. 91, 162902 (2007); http://dx.doi.org/10.1063/1.2798498 (3 pages) | Cited 22 times

Online Publication Date: 15 October 2007

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Dysprosium- and scandium-doped HfO2 films have been deposited by atomic-vapor deposition on SiO2/Si substrates. Glancing-incidence x-ray diffraction demonstrates that Dy0.10Hf0.90Ox and Sc0.10Hf0.90Ox films show a cubic crystal structure, whereas HfO2 films are monoclinic. The dielectric permittivity increases strongly from 16 for HfO2 to 32 for Dy0.10Hf0.90Ox and Sc0.10Hf0.90Ox. This leads to a reduction of the leakage current in the tunneling regime by up to three orders of magnitude for constant effective oxide thickness. For thick films (≳6 nm), it is shown that leakage occurs via the Poole-Frenkel mechanism and that doping HfO2 increases leakage for constant physical oxide thickness.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.A- Nucleation and growth
77.22.Ch Permittivity (dielectric function)
73.50.Fq High-field and nonlinear effects

Separate control of direct and converse piezoelectric effects in flexoelectric piezoelectric composites

John Y. Fu and L. Eric Cross

Appl. Phys. Lett. 91, 162903 (2007); http://dx.doi.org/10.1063/1.2790476 (3 pages) | Cited 7 times

Online Publication Date: 17 October 2007

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The fabrication of piezoelectric composites driven by the flexoelectric charge separation has aroused considerable interest recently. In earlier oral presentations, we have posited that, in such composites, even though the direct and the converse flexoelectric effects are thermodynamically equivalent, it is possible to separately control the direct and converse piezoelectricities. Here, we would like to demonstrate how this separation can be accomplished through the control of the texture symmetry and that the result does not violate reciprocity as two different phases are involved in those two effects.
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77.84.Lf Composite materials
77.65.-j Piezoelectricity and electromechanical effects

High Tc lead-free BaTiO3–(Bi1/2Na1/2)TiO3 positive temperature coefficient of resistivity ceramics with electrically heterogeneous structure

Ping-Hua Xiang, Hiroaki Takeda, and Tadashi Shiosaki

Appl. Phys. Lett. 91, 162904 (2007); http://dx.doi.org/10.1063/1.2799878 (3 pages) | Cited 14 times

Online Publication Date: 17 October 2007

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A distinct positive temperature coefficient of resistivity effect has been observed in BaTiO3–(Bi1/2Na1/2)TiO3 (BT-BNT) ceramics sintered in a N2 flow with low O2 concentration. With the addition of BNT, the samples exhibit resistivity jumps of ∼ 103–105 starting at ∼ 190–210 °C. X-ray diffraction results indicate that the BNT phase and BT phase formed a solid solution during sintering. An electrically heterogeneous structure, consisting of the grain interiors, outer grain shells, and grain boundaries, is revealed by the complex impedance analyses. The observed dc resistivity jump is attributed to the rapid resistivity rise in both grain boundaries and grain shells.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Sk Insulators
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.72.Mm Grain and twin boundaries

Correlation between structural deformation and magnetoelectric response in (1−x) Pb(Zr0.52Ti0.48)O3–xNiFe1.9Mn0.1O4 particulate composites

Rashed Adnan Islam, Jiechao Jiang, Feiming Bai, Dwight Viehland, and Shashank Priya

Appl. Phys. Lett. 91, 162905 (2007); http://dx.doi.org/10.1063/1.2799261 (3 pages) | Cited 10 times

Online Publication Date: 17 October 2007

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The ferroelectric, ferromagnetic, and magnetoelectric properties of (1−x) Pb(Zr0.52Ti0.48)O3–xNiFe1.9Mn0.1O4 (PZT-NFM) ceramic composites were found to be dependent upon postsinter annealing and aging. It was found on annealing and aging that (i) the size and density of the NFM phase is reduced, (ii) the PZT lattice constants changed from (a = 3.87 Å, c = 4.07 Å) to (a = 4.07 Å, c = 4.09 Å), (iii) the ferroelectric and ferromagnetic Curie temperatures decreased by 8 and 33 °C, respectively, and (iv) the magnetoelectric coefficient increased by ∼ 50%.
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77.84.Lf Composite materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
75.50.Dd Nonmetallic ferromagnetic materials
77.80.Dj Domain structure; hysteresis
75.80.+q Magnetomechanical effects, magnetostriction
61.66.Fn Inorganic compounds

Dielectric anomalies in (BaxSr1−x)4Nd2Ti4Nb6O30 ceramics with various radius differences between A1- and A2-site ions

X. L. Zhu, S. Y. Wu, and X. M. Chen

Appl. Phys. Lett. 91, 162906 (2007); http://dx.doi.org/10.1063/1.2800789 (3 pages) | Cited 14 times

Online Publication Date: 18 October 2007

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Dielectric response of tetragonal tungsten bronze dielectrics (BaxSr1−x)4Nd2Ti4Nb6O30 was investigated over a broad temperature and frequency range, and the obvious composition-dependent dielectric anomalies with respect to x value were discussed in detail in association with the radius differences between A1- and A2-site ions. With decreasing the magnitude of radius difference between A1- and A2-site ions, the normal ferroelectric peak above 400 K became weaker, and two relaxor peaks at lower temperatures became obvious. The low- and high-temperature relaxor behaviors, which followed well the Vogel-Fulcher relationship, were associated with the polar clusters caused by the off-center Nb/Ti displacements and the incommensurate tilting modulation, respectively.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ch Permittivity (dielectric function)

Characterizing the effects of disorder in metamaterial structures

Jonah Gollub, Thomas Hand, Soji Sajuyigbe, Shawn Mendonca, Steve Cummer, and David R. Smith

Appl. Phys. Lett. 91, 162907 (2007); http://dx.doi.org/10.1063/1.2801391 (3 pages) | Cited 15 times

Online Publication Date: 19 October 2007

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We investigate the effects of disorder on metamaterial samples composed of split ring resonators with randomly introduced variation in their geometrical dimensions. We demonstrate that disorder broadens the negative permeability band and introduces effective losses into the system. Transmission measurements on samples with varying degrees of disorder are found to be in excellent agreement with predictions based on standard homogenization theories.
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42.79.-e Optical elements, devices, and systems

Bilayer model of polarization offset of compositionally graded ferroelectric thin films

J. Zhang, M. H. Tang, J. X. Tang, F. Yang, H. Y. Xu, W. F. Zhao, X. J. Zheng, Y. C. Zhou, and J. He

Appl. Phys. Lett. 91, 162908 (2007); http://dx.doi.org/10.1063/1.2800819 (3 pages) | Cited 4 times

Online Publication Date: 19 October 2007

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The anomalous vertical shift behavior of hysteresis loops observed in compositionally graded ferroelectric films was investigated using an analytical bilayer model. By introducing a parameter A which is defined by grad(c)/c(0), the model demonstrated that the compositional graded structure is sufficient to allow for the hysteresis loop shift along the polarization axis, and the shift is affected significantly by the concentration distribution in the films. Two reversed electric field buildups were also observed in the layers as indicated by the E-t profile.
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77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

High-oxygen-pressure crystal growth of ferroelectric Bi4Ti3O12 single crystals

Katsuya Yamamoto, Yuuki Kitanaka, Muneyasu Suzuki, Masaru Miyayama, Yuji Noguchi, Chikako Moriyoshi, and Yoshihiro Kuroiwa

Appl. Phys. Lett. 91, 162909 (2007); http://dx.doi.org/10.1063/1.2800822 (3 pages) | Cited 16 times

Online Publication Date: 19 October 2007

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We have investigated the effects of high-oxygen-pressure crystal growth of ferroelectric Bi4Ti3O12 on the polarization properties along the a(b) axis. Domain observations by piezoresponse force microscope demonstrate that a small remanent polarization (Pr) for the crystals grown at 0.02 MPa is attributed to the clamping of 90° domain walls by oxygen vacancies. The vacancy formation of Bi and O during crystal growth at high temperatures is suppressed at a higher oxygen pressure, leading to a larger Pr of 47 μC/cm2 for the crystals grown at 1 MPa oxygen. High-oxygen-pressure sintering is proposed to be effective for obtaining Bi4Ti3O12-based devices with enhanced polarization properties.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.10.Dn Growth from solutions
62.50.-p High-pressure effects in solids and liquids
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
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