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1 Sep 2000

Volume 88, Issue 5, pp. 2187-3105

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Voltage-dependent dielectric breakdown and voltage-controlled negative resistance in anodized Al–Al2O3–Au diodes

T. W. Hickmott

J. Appl. Phys. 88, 2805 (2000); http://dx.doi.org/10.1063/1.1287116 (8 pages) | Cited 32 times

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Theories of dielectric breakdown in insulating films normally assume that dielectric breakdown depends on the electric field in the sample; that is, the thicker the film the higher the breakdown voltage. Contrary to theoretical expectations, voltage-dependent dielectric breakdown is observed in Al–Al2O3–Au diodes where Al2O3 is made by anodizing in different electrolytes. The breakdown voltage is ∼4.5 V, independent of Al2O3 thickness and anodizing electrolyte. Voltage-controlled negative resistance (VCNR) develops in the current–voltage (I–V) characteristics of Al–Al2O3–Au diodes after voltage-dependent breakdown. Electron emission into vacuum accompanies the formation of VCNR in the I–V characteristics. Detailed studies of the development of VCNR show that the maximum current, the voltage for maximum current, and the voltage threshold for electron emission depend on the maximum voltage applied to the sample. A large current increase occurs for maximum applied voltage between 5 and 7 V. A fully developed VCNR characteristic has an ohmic contact suggesting that the development of an ohmic contact at a metal–insulator interface initiates breakdown. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Rw Metal-insulator-metal structures

Raman study of the ordering in Sr(B0.5′Nb0.5)O3 compounds

R. Ratheesh, M. Wöhlecke, B. Berge, Th. Wahlbrink, H. Haeuseler, E. Rühl, R. Blachnik, P. Balan, N. Santha, and M. T. Sebastian

J. Appl. Phys. 88, 2813 (2000); http://dx.doi.org/10.1063/1.1287762 (6 pages) | Cited 41 times

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Strontium based complex perovskites are potential candidates for microwave integrated circuit applications. In the present article, we report on Raman scattering studies of cubic and noncubic structures of Sr(B0.5′Nb0.5)O3 [B′=Ga, In, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Yb] based complex-perovskite materials for an improved understanding of structure-property relations. The spectral results are compared to some tantalum analogues of known crystal structure. The present study reveals a higher degree of ordering for the tantalum compounds compared to those of the niobium analogues. Vibrational studies show a correlation between the tolerance factor and symmetry of these materials. © 2000 American Institute of Physics.
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61.66.Fn Inorganic compounds
78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Ferroelectric Bi4Ti3O12 thin films on Pt-coated silicon by halide chemical vapor deposition

Mikael Schuisky, Anders Hårsta, Sergey Khartsev, and Alex Grishin

J. Appl. Phys. 88, 2819 (2000); http://dx.doi.org/10.1063/1.1288499 (6 pages) | Cited 3 times

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A halide chemical vapor deposition technique has been developed to grow highly c-axis oriented submicron Bi4Ti3O12 films onto Pt(200 nm)/Ti(20 nm)/SiO2(1200 nm)/Si(100) substrates. BiI3, TiI4, and oxygen were used as precursors. The total gas pressure was found to be the critical processing parameter to grow films with good crystalline and dielectric properties. The 300 nm thick Bi4Ti3O12 films fabricated at 700 °C and total gas pressure of 3.8 Torr exhibit the best dielectric performance: dielectric constant around 200 and loss tan δ∼0.018 at 100 kHz, remnant polarization of 5.3 μC/cm2, induced polarization of 14.9 μC/cm2 at 560 kV/cm, coercive field of 150 kV/cm, electrical tunability of 51% at 350 kV/cm, resistivity of 2×109 Ω cm, and leakage current as low as 3×10−5 A/cm2 at 100 kV/cm. The effect of weak reduction of the remnant polarization and coercive field has been observed in the temperature range from 300 to 77 K and ascribed to the in-plane orientation of the polar a axis in fabricated Bi4Ti3O12 films. © 2000 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
73.61.Ng Insulators
72.20.Fr Low-field transport and mobility; piezoresistance

Effect of excess Bi2O3 on the ferroelectric properties of SrBi2Ta2O9 ceramics

Jung-Kun Lee, Byungwoo Park, and Kug-Sun Hong

J. Appl. Phys. 88, 2825 (2000); http://dx.doi.org/10.1063/1.1286062 (5 pages) | Cited 9 times

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In this study, the effect of bismuth content on phase-transition behavior, ferroelectric property, and crystal structure of strontium–bismuth–tantalate (SBT) ceramics was explored with the aid of ϵr(T), ferroelectric hysteresis loop, x-ray diffraction (XRD), and Raman spectroscopy. Both the phase-transition behavior and ferroelectric properties such as spontaneous polarization (Ps) showed a dependence on Bi content. The ferroelectric Curie temperature Tc, was found to decrease with increasing the Bi content and Ps was maximized when 2–3 mol % excess Bi2O3 was added. It was found that Raman spectroscopy and XRD can explain the Bi-content dependence of SBT ceramics. The frequency and the width of the mode below 60 cm−1 in Raman spectra revealed that a site exchange of Sr2+ and Bi3+ ions occurred. The formation of antisite defects was confirmed by the change in the intensity ratio of I(008)/I(105) in the XRD patterns. The calculation of structure factors showed it was also related to antisite defects (SrBi,BiSr). © 2000 American Institute of Physics.
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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
78.30.Hv Other nonmetallic inorganics
61.72.J- Point defects and defect clusters
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Low-loss Ba0.5Sr0.5TiO3 thin films by inverted cylindrical magnetron sputtering

E. J. Cukauskas, Steven W. Kirchoefer, and J. M. Pond

J. Appl. Phys. 88, 2830 (2000); http://dx.doi.org/10.1063/1.1289052 (6 pages) | Cited 10 times

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The structural and electrical characteristics of Ba0.5Sr0.5TiO3 (BST) thin films deposited by inverted cylindrical magnetron rf sputtering have been investigated. This unconventional sputter deposition technique consisting of a hollow cylindrical composite target of BST, high argon/oxygen gas pressure 53.2 Pa (400 μm), and 750 °C substrate temperature was employed for depositing low-loss BST thin films. The films were postannealed in a tube furnace at 780 °C for 8 h in flowing oxygen. Atomic-force microscopy revealed anisotropic grain growth with a columnar grain structure protruding from the surface with a 0.25 μm grain size. X-ray diffractometry shows the films to be purely (h00) oriented for certain deposition parameters. The lattice parameter of the best film was slightly larger than that for bulk BST. Other deposition conditions yielded films having many of the BST powder peaks. Capacitance versus voltage characteristics have been measured from 50 MHz to 20 GHz. Device Q values >600, beyond the resolution of the device/measurement system, were realized with a 6.7% tunability at 10 GHz for the best films.
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81.15.Cd Deposition by sputtering
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.22.Gm Dielectric loss and relaxation
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Relaxational polarization in polar dielectric barium magnesium niobate

Surya M. Gupta, E. Furman, E. Colla, Z. Xu, and Dwight Viehland

J. Appl. Phys. 88, 2836 (2000); http://dx.doi.org/10.1063/1.1287774 (7 pages) | Cited 6 times

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Relaxor-like dielectric behavior, analogous to that found in lead magnesium niobate, has been induced in the polar dielectric barium magnesium niobate (BMN). In BMN, the dielectric constant was increased and the temperature of the maximum dielectric constant was shifted to a lower temperature with a decrease in measurement frequency with increasing A-site vacancy concentrations. The frequency dispersion of the permittivity maximum exhibited good agreement with the Arrhenius relationship. An activation energy of 0.15 eV and a preexponential factor 1014 s−1 were determined. No frequency dispersion in the imaginary part of the permittivity was found below the temperature of the dielectric maximum. A linear polarization-electric field dependence was observed at room temperature. A polarization of 0.3 μC/cm2 was found under a field of 75 kV/cm at 25 °C. Phase analysis revealed a single phase perovskite structure with a hexagonal unit cell with a=5.77 Å and c=7.08 Å. 〈110〉 selected area electron diffraction patterns revealed superlattice reflections along the 〈111〉. High resolution Z-contrast imaging was used to study the local ordering and the origin of the relaxational polarization. © 2000 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
61.72.J- Point defects and defect clusters
61.66.Fn Inorganic compounds
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