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8 May 2000

Volume 76, Issue 19, pp. 2647-2800

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Ferroelectricity in a pure BiFeO3 ceramic

M. Mahesh Kumar, V. R. Palkar, K. Srinivas, and S. V. Suryanarayana

Appl. Phys. Lett. 76, 2764 (2000); http://dx.doi.org/10.1063/1.126468 (3 pages) | Cited 224 times

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The difficulties in synthesizing phase pure BiFeO3 are well known. In this letter we are reporting the optimized synthesis conditions for obtaining phase pure BiFeO3 ceramic. The oxide mixing technique followed by leaching with dilute nitric acid has been used for the synthesis. X-ray diffraction pattern indicated that the sample is phase pure. Scanning electron microscopy along with energy dispersive x-ray fluorescence analysis confirmed the chemical homogeneity of the sample. No segregation of the impurity phase in the matrix was detected. Moreover, Bi/Fe atomic ratio is observed to be ∼1. The ferroelectric transition of the sample at 836 °C has been detected by differential thermal analysis. © 2000 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.80.B- Phase transitions and Curie point

Microscopic model of ferroelectricity in stress-free PbTiO3 ultrathin films

Ph. Ghosez and K. M. Rabe

Appl. Phys. Lett. 76, 2767 (2000); http://dx.doi.org/10.1063/1.126469 (3 pages) | Cited 111 times

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The ground-state polarization of PbTiO3 thin films is studied using a microscopic effective Hamiltonian with parameters obtained from first-principles calculations. Under short-circuit electrical boundary conditions, (001) films with thickness as low as three unit cells are found to have a perpendicularly polarized ferroelectric ground state with significant enhancement of the polarization at the surface. © 2000 American Institute of Physics.
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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.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization

Neutron intrinsic gettering on electrical property of gate oxynitride in metal-oxide-Si capacitor

Kuei-Shu Chang-Liao, Nan-Kuang Yi, and Jenn-Gwo Huang

Appl. Phys. Lett. 76, 2770 (2000); http://dx.doi.org/10.1063/1.126470 (3 pages) | Cited 2 times

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The electrical property of gate oxynitride in metal-oxide-Si capacitor is improved by a neutron-intrinsic-gettering (NIG) treatment. This improvement can be attributed to the reduction of nitrogen concentration in the oxynitride bulk and the decrease of interstitial oxygen defect in the silicon. For the oxynitride formed using NIG-treated Si substrate, the breakdown electric field is increased and the reliability is improved. A significant improvement of electrical property in gate oxynitride is observed by a NIG treatment including a fast neutron dose of 7.2×1016 cm−2 and an anneal at 1100 °C for 6 h. This NIG treatment would be promising for the improvement of electrical properties in gate oxynitrides. © 2000 American Institute of Physics.
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84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Hg Neutron radiation effects
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
77.22.Jp Dielectric breakdown and space-charge effects

Glassy to inhomogeneous-ferroelectric crossover in (Pb, La)(Zr, Ti)O3 ceramics

V. Bobnar, Z. Kutnjak, and A. Levstik

Appl. Phys. Lett. 76, 2773 (2000); http://dx.doi.org/10.1063/1.126471 (3 pages) | Cited 27 times

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The temperature dependence of the dielectric nonlinearity a3 = ε3/ε14 has been determined in 9/65/35 (Pb, La)(Zr, Ti)O3 ceramics. In zero electric field a deep in the temperature behavior of the static a3 has been observed indicating a crossover from paraelectric-like to glass-like behavior on cooling towards the freezing transition. By varying a bias electric field another glass-to-ferroelectric crossover has been observed in the temperature dependence of the static a3. The observed crossovers as well as the temperature dependence of the linear static dielectric constant agree with the predictions of the spherical random-bond–random-field model of relaxor ferroelectrics. © 2000 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.B- Phase transitions and Curie point

Pyroelectric or piezoelectric compensated ferroelectric composites

Beatrix Ploss, Bernd Ploss, F. G. Shin, H. L. W. Chan, and C. L. Choy

Appl. Phys. Lett. 76, 2776 (2000); http://dx.doi.org/10.1063/1.126472 (3 pages) | Cited 36 times

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The matrix and inclusions of 0–3 composites of lead titanate (PT) in polyvinylidenefluoride trifluoroethylene (P(VDF–TrFE)) have been independently poled by a special poling method. The polarization states of both constituents are investigated by the measurement of the dynamic pyroelectric coefficients of the composites in the temperature range of 20–90 °C, within which the copolymer matrix undergoes a ferroelectric-paraelectric phase change. The pyroelectric coefficients of PT and P(VDF–TrFE) have the same sign, while their piezoelectric coefficients have opposite signs. This allows the preparation of composites with enhanced pyroelectric but reduced piezoelectric activity when the matrix and inclusions are polarized in the same direction, or vice versa if the constituents are oppositely polarized. For a PT volume fraction of 27% it was possible to prepare a pyroelectric composite with vanishing piezoelectric activity or a piezoelectric composite with vanishing pyroelectric activity by poling the matrix and inclusions in parallel or antiparallel directions. © 2000 American Institute of Physics.
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77.84.Lf Composite materials
77.70.+a Pyroelectric and electrocaloric effects
77.22.Ej Polarization and depolarization
77.65.Bn Piezoelectric and electrostrictive constants
77.80.-e Ferroelectricity and antiferroelectricity

Dielectric enhancement and ferroelectric anomaly of compositionally graded (Pb, Ca)TiO3 thin films derived by a modified sol–gel technique

Dinghua Bao, Xi Yao, and Liangying Zhang

Appl. Phys. Lett. 76, 2779 (2000); http://dx.doi.org/10.1063/1.126473 (3 pages) | Cited 42 times

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Compositionally graded (Pb, Ca)TiO3 thin films were prepared on platinum-coated silicon substrates by a monoethanolamine-modified sol–gel technique. The crystalline orientation and surface morphology of the graded films were related to the deposition sequence of the film layer. The dielectric constants, for up-graded and down-graded films annealed at 600 °C for 60 min were found to be 504 and 399, respectively. Both were larger than those reported for conventional (Pb, Ca)TiO3 thin films. The compositionally graded films had large polarization offsets in hysteresis loops when driven by an alternating electric field. The magnitude of polarization offsets displayed a power-law dependence on the electric field, and the direction of the offsets depended on the direction of the composition gradient with respect to the substrate. The offset, 120 μC/cm2 at 300 kV/cm driving electric field, was obtained. These results showed that compositionally graded (Pb, Ca)TiO3 thin films had enhanced dielectric properties and abnormal ferroelectric properties which can be used in various microelectronic devices. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.55.Nq Composition and phase identification
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
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