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16 Oct 2000

Volume 77, Issue 16, pp. 2437-2616

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High nonlinearity of Ba0.6Sr0.4TiO3 films heteroepitaxially grown on MgO substrates

B. H. Park, Y. Gim, Y. Fan, Q. X. Jia, and P. Lu

Appl. Phys. Lett. 77, 2587 (2000); http://dx.doi.org/10.1063/1.1318233 (3 pages) | Cited 62 times

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We have heteroepitaxially deposited Ba0.6Sr0.4TiO3 (BST) thin films on (001)-oriented MgO substrates using pulsed-laser deposition. By optimizing the deposition temperature and adjusting the film thickness, we have successfully increased the dielectric nonlinearity and decreased the dielectric loss of BST films. BST thin films grown at 750 °C with a thickness of 1.1 μm showed a dielectric constant tunability of greater than 65% and a tunability/loss of 43 at a surface electric field of 80 kV/cm at room temperature. X-ray diffraction and transmission electron microscopy analyses indicated that the tunability and dielectric loss were closely related to the crystallinity of the BST films. © 2000 American Institute of Physics.
Show PACS
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
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
81.15.Fg Pulsed laser ablation deposition

Degradation of ferroelectric Pb(Zr, Ti)O3 under reducing conditions

Y. Shimakawa and Y. Kubo

Appl. Phys. Lett. 77, 2590 (2000); http://dx.doi.org/10.1063/1.1318240 (3 pages) | Cited 14 times

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The degradation mechanisms of Pb(Zr, Ti)O3 (PZT) under reducing conditions were investigated. Although no apparent changes were seen from the results of thermogravimetric and x-ray diffraction measurements after H2 annealing at typical process temperatures, the PZT material had changed: The sample appearance changed from white to black. A small amount of PZT (less than 0.3% even after 4% H2 annealing at 550 °C) decomposed into Pb in the reducing atmosphere. This, however, was too little to cause all of the change in the sample appearance. Systematic changes in the lattice constants and the black color of the sample strongly suggest that oxygen defects were introduced into the PZT during H2 annealing. Oxygen defects would produce a donor level within the PZT band gap, which would account for the change in color, and would increase leakage current in capacitors. We have also found that PbZrO3 decomposed through oxygen dissociation more easily than PbTiO3. Oxygen atoms in PbZrO3 are weakly bonded to Zr compared to Ti–O bonds in PbTiO3 due to a significant antibonding component in the hybridized orbitals. © 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.-e Ferroelectricity and antiferroelectricity
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
71.55.Ht Other nonmetals
61.50.Lt Crystal binding; cohesive energy

(BaxSr1−x)Ti1+yO3+z interface contamination and its effect on electrical properties

Jaemo Im, S. K. Streiffer, Orlando Auciello, and Alan R. Krauss

Appl. Phys. Lett. 77, 2593 (2000); http://dx.doi.org/10.1063/1.1318730 (3 pages) | Cited 26 times

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Surface contamination and cleaning processes of (BaxSr1−x)Ti1+yO3+z(BST) and Pt films were investigated using in situ, real-time mass spectroscopy of recoiled ions (MSRI). MSRI analysis revealed that BST film surfaces exposed to atmospheric ambient are contaminated with carbon and hydrogen containing species, which could be removed by thermal decomposition/desorption in an oxygen ambient. Cleaning of the BST surface was accomplished by annealing at 500 °C in ⩾1 mTorr O2, resulting in complete elimination of these species. Similar contamination on Pt film surfaces could be eliminated with only 200 °C annealing in 5×10−4 Torr of O2. Annealing of the BST film surface in oxygen prior to deposition of the top Pt electrode results in a clean top Pt/BST interface that yields BST capacitors with much lower and more symmetric leakage current characteristics, and lower dielectric losses compared to BST capacitors with contaminated top Pt electrode/BST interfaces. © 2000 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
81.65.Cf Surface cleaning, etching, patterning
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.22.Gm Dielectric loss and relaxation
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.40.Gh Other heat and thermomechanical treatments

Curie–Weiss-type law for the strain and stress effects on the dielectric response of ferroelectric thin films

N. A. Pertsev, V. G. Koukhar, R. Waser, and S. Hoffmann

Appl. Phys. Lett. 77, 2596 (2000); http://dx.doi.org/10.1063/1.1318934 (3 pages) | Cited 27 times

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Variations of the dielectric properties of ferroelectric thin films with the misfit strain Sm in the film/substrate system and the associated biaxial stress σ inside the film are analyzed theoretically. Calculations are performed in a mean-field approximation for the dielectric response displayed in a plate-capacitor setup by single crystalline films epitaxially grown on tensile substrates (Sm>0). It is shown that, in the absence of misfit-strain-induced phase transitions, the film dielectric susceptibility η33 obeys the Curie–Weiss-type law η33(Sm) = ε0KS/(Sm−Sm∗), η33(σ) = ε0Kσ/(σ−σ∗). Theoretical predictions are compared with the measured stress dependence of the dielectric response of polycrystalline Ba0.7Sr0.3TiO3 films grown on Pt/SiO2/Si. The theory explains the observed dielectric behavior and predicts the existence of in-plane polarization state in this film/substrate system. © 2000 American Institute of Physics.
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77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
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.Ej Polarization and depolarization

Ionic Wiedemann–Franz law

J. F. Scott, H. G. Bohn, and W. Schenk

Appl. Phys. Lett. 77, 2599 (2000); http://dx.doi.org/10.1063/1.1318939 (2 pages)

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The Wiedemann–Franz law for electron transport in metals was historically a linch pin for the free-electron theory of metals; it states that, at moderately low temperatures, the ratio of thermal conductivity K to electrical conductivity σ is proportional to absolute temperature, with a proportionality constant called “the Lorenz number” of L = 2.45×10−8 W Ω/K2. Here we describe work on yttrium-stabilized zirconia in which we have found that a similar relationship is valid above 1350 K, where nearly all the electrical conduction and thermal conduction arise from ionic currents. © 2000 American Institute of Physics.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
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