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28 Jan 2002

Volume 80, Issue 4, pp. 535-701

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Ferroelectric properties of laser-ablated Sr1−xAxBi2Ta2O9 thin films (where A = Ba, Ca)

Rasmi R. Das, P. Bhattacharya, W. Pérez, Ram S. Katiyar, and Seshu B. Desu

Appl. Phys. Lett. 80, 637 (2002); http://dx.doi.org/10.1063/1.1436528 (3 pages) | Cited 19 times

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Bismuth-layered ferroelectric thin films of Sr1−xAxBi2Ta2O9, with composition x = 0 and 0.2, were fabricated by using the pulsed-laser deposition technique. Structural characterization of the films by x-ray diffraction and atomic force microscopy, revealed that the films are polycrystalline in nature with average grain size of 180 nm. The films displayed spherical grains with a surface roughness of 12 nm. The ferroelectric measurements of Sr0.8Ba0.2Bi2Ta2O9, SrBi2Ta2O9, and Sr0.8Ca0.2Bi2Ta2O9 showed saturated hysteretic behavior with remanent polarization (2Pr) of 23.5, 17.9, 14 μC/cm2 and coercive field (Ec) of 31.06, 74.2, 86.3 kV/cm for a maximum applied electric field of 360 kV/cm. Films exhibited minimal ( ⩽ 17%) degradation of polarization for up to 1010 switching cycles. It was observed that the coercive field decreased with increase in the ionic size of partially substituted cations. The leakage current density of films were found to be of the order of ∼ 10−8 A/cm2 for up to a breakdown field of about 75 kV/cm. © 2002 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
81.15.Fg Pulsed laser ablation deposition
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
77.22.Jp Dielectric breakdown and space-charge effects
77.80.Dj Domain structure; hysteresis

Dielectric properties of 1 MeV electron-irradiated polyimide

P. S. Alegaonkar, V. N. Bhoraskar, P. Balaya, and P. S. Goyal

Appl. Phys. Lett. 80, 640 (2002); http://dx.doi.org/10.1063/1.1435408 (3 pages) | Cited 5 times

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The dielectric parameters of 50-μm-thick polyimide samples irradiated in air with 1 MeV electrons and in BF3 solution with Co-60 gamma rays were studied. The dielectric constant of polyimide was found to decrease with increasing electron fluence and dose of gamma rays. At an electron fluence of ∼ 1015 e/cm2, the dielectric constant decreased from its virgin value of 3.15 to 2.4, measured at a frequency of ∼ 7 MHz. Furthermore, by irradiating polyimide samples in BF3 solution with gamma rays, boron and fluorine diffused into each polyimide sample from both sides. In these polyimide samples, the dielectric constant decreased further to ∼ 2.1 (7 MHz). In a plot of dielectric loss, ϵ″, vs log (f ), two peaks were observed over a frequency range 100 Hz–7 MHz, in virgin as well as in the electron- and gamma-ray-irradiated polyimide samples. The dielectric loss increased with increasing electron fluence or dose of gamma rays. The refractive index (632.8 nm) of polyimide decreased from the virgin value of 1.74 to 1.69, at an electron fluence of ∼ 1015 e/cm2. The observed decrease in the dielectric constant and the refractive index can be attributed to the induced changes in the polarization and density of the irradiated polyimide samples. © 2002 American Institute of Physics.
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77.84.Jd Polymers; organic compounds
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.80.Fe Electron and positron radiation effects
61.82.Pv Polymers, organic compounds

Dielectric and conduction behavior of La-doped SrTiO3 with suppressed quantum-paraelectric background

Zhi Yu and Chen Ang

Appl. Phys. Lett. 80, 643 (2002); http://dx.doi.org/10.1063/1.1435409 (3 pages) | Cited 8 times

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The dielectric and conduction behavior of La-doped SrTiO3 annealed in different atmospheres was studied. The results showed that the quantum-paraelectric behavior was purely suppressed by La doping. A variable-range-hopping conduction was observed for the samples annealed in a strongly reducing atmosphere, and subsequently an insulator-metal transition occurred. The possible correlation of the singular dielectric behavior and the electrical conduction behavior is pointed out. The validity of the Barrett relation derived from the mean-field theory for quantum paraelectrics is discussed. © 2002 American Institute of Physics.
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72.60.+g Mixed conductivity and conductivity transitions
71.30.+h Metal-insulator transitions and other electronic transitions
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Ga Transition-metal compounds
61.72.Cc Kinetics of defect formation and annealing
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Correlation radius of polarization fluctuations in the disordered ferroelectrics

M. D. Glinchuk, E. A. Eliseev, V. A. Stephanovich, E. V. Kirichenko, and L. Jastrabik

Appl. Phys. Lett. 80, 646 (2002); http://dx.doi.org/10.1063/1.1430266 (3 pages) | Cited 6 times

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We calculate correlation radius of polarization fluctuations in the disordered ferroelectrics. The consideration is performed in the model suitable for relaxor ferroelectrics. We consider reference Burns phase in a mean field approximation subjected to random electric field E. The “entire relaxor” is then obtained by averaging of characteristics of the reference phase with distribution function of the random field. For correlation radius (Rc) calculation we take into account the damping of the reference phase soft mode and its dependence on E and perform the averaging over the random field distribution. The obtained temperature dependence of Rc is shown to be strongly dependent on the decay parameter. It appears to be completely different for the disordered system either in the dipole-glass state or in mixed ferroglass phase. The fitting of calculated and measured Rc(T) in PbMg1/3Nb2/3O3 is performed. © 2002 American Institute of Physics.
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77.22.Ej Polarization and depolarization
77.80.-e Ferroelectricity and antiferroelectricity

Dielectric constant of boron carbon nitride films synthesized by plasma-assisted chemical-vapor deposition

Takashi Sugino, Yoshihiro Etou, Tomoyoshi Tai, and Hirotaro Mori

Appl. Phys. Lett. 80, 649 (2002); http://dx.doi.org/10.1063/1.1436522 (3 pages) | Cited 9 times

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Polycrystalline boron carbon nitride (BCN) films are synthesized at various temperatures by plasma-assisted chemical-vapor deposition. BCN films are characterized by x-ray photoelectron spectroscopy, transmission electron microscopy, and transmission electron diffraction. The dielectric constant is estimated from the accumulation region of capacitance–voltage (C–V) characteristics of Au/BCN/p-Si samples. Reduction in the crystal grain size and increase of the amorphous region of the BCN film are observed with decreasing growth temperature. The dielectric constant is found to decrease with decreasing growth temperature. A dielectric constant as low as 2.4 is achieved for the BCN film. © 2002 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
79.60.Dp Adsorbed layers and thin films
68.55.-a Thin film structure and morphology

Crystal orientation dependence of the piezoelectric d33 coefficient in tetragonal BaTiO3 as a function of temperature

Dragan Damjanovic, Franziska Brem, and Nava Setter

Appl. Phys. Lett. 80, 652 (2002); http://dx.doi.org/10.1063/1.1445481 (3 pages) | Cited 28 times

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Using the Landau–Ginzburg–Devonshire approach, the longitudinal piezoelectric coefficient in an arbitrary direction, d33∗(θ), was calculated as a function of temperature in tetragonal BaTiO3 crystals. The direction along which d33∗(θ) is maximum is a function of piezoelectric dij coefficients referred to the crystallographic coordinate system. Below a critical ratio of the shear and longitudinal coefficients, d15/d33, the maximum d33∗(θ) lies along the [001] axis. As the low-temperature orthorhombic phase is approached on cooling, the d15 increases, reflecting softening of the lattice along the axis of the incipient orthorhombic distortion, and the direction of maximum d33∗(θ) deviates significantly from the [001] axis. Our results suggest that the enhanced d33∗(θ) coefficient along a direction other than the polar axis recently reported in some ferroelectrics is at least in part controlled by these intrinsic lattice effects. © 2002 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
64.70.K- Solid-solid transitions

Electrical conduction mechanism in high-dielectric-constant (Ba0.5,Sr0.5)TiO3 thin films

Shao-Te Chang and Joseph Ya-min Lee

Appl. Phys. Lett. 80, 655 (2002); http://dx.doi.org/10.1063/1.1436527 (3 pages) | Cited 42 times

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The electrical conduction mechanism of (Ba0.5,Sr0.5)TiO3 (BST) as a function of the temperature was studied. Au/BST/Pt metal–insulator–metal capacitors were fabricated. The temperature range was from 300 to 423 K. The conduction current depended on the voltage polarity. At high electrical field (>800 kV/cm) and with the Pt electrode biased negatively, the Pt/BST interface forms a Schottky barrier with a barrier height of 0.58 eV from 300 to 373 K. The Au/BST interface forms an ohmic contact. The conduction current when the Au electrode is biased negatively shows space-charge-limited-current behavior. An energy band diagram is proposed to explain the experimental results. © 2002 American Institute of Physics.
Show PACS
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.22.Jp Dielectric breakdown and space-charge effects
84.32.Tt Capacitors
73.40.Rw Metal-insulator-metal structures
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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