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24 Jul 1989

Volume 55, Issue 4, pp. 325-411

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Weak flux pinning at grain boundaries in Ag sheathed Ba2YCu3O6+x tapes

K. Osamura, T. Takayama, and S. Ochiai

Appl. Phys. Lett. 55, 396 (1989); http://dx.doi.org/10.1063/1.102423 (3 pages) | Cited 7 times

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This letter is concerned with the mechanism controlling the transport critical current measured at 4.2 K. The current densities increased with decreasing the oxide layer thickness of Ag sheathed tapes and reached 1010 A/cm2 at 15 T for the tape with a 15‐μm‐thick layer. The magnetic field dependence of critical current density in the region between 0.5 and 15 T can be explained in terms of a modified model of the theory by E. J. Kramer [J. Appl. Phys. 44, 1360 (1973)], based on the weak flux pinning along grain boundaries.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Evidence for enhancement of critical current by intergrain Ag in YBaCuO‐Ag ceramics

B. Dwir, M. Affronte, and D. Pavuna

Appl. Phys. Lett. 55, 399 (1989); http://dx.doi.org/10.1063/1.102424 (3 pages) | Cited 69 times

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We report the evidence for enhancement of critical current density Jc by ∼50%, which occurs when ∼10 wt. % Ag is added to Y1Ba2Cu3O7−δ ceramics. The maximal Jc (∼700 A/cm2 at T=77 K) appears simultaneously with maximum YBaCuO compactness in the samples. The silver fills the intergranular space (holes) without Cu substitution, and the critical temperature Tc is not reduced from the bulk value (∼91 K). Normal‐state resistivity of Ag‐YBaCuO samples is decreased by an order of magnitude, and samples exhibit improved contact resistance and resistance to water. While the critical density is improved by adding ∼10 wt. % Ag, it decreases at higher Ag concentrations.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates

Electron‐phonon relaxation rate in single‐crystal lanthanum cuprate

G. L. Doll, G. L. Eesley, S. D. Brorson, M. S. Dresselhaus, G. Dresselhaus, A. Cassanho, H. P. Jenssen, and D. R. Gabbe

Appl. Phys. Lett. 55, 402 (1989); http://dx.doi.org/10.1063/1.102425 (3 pages) | Cited 4 times

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We report the results of phonon relaxation processes obtained from picosecond transient thermoreflectance measurements of single‐crystal La2CuO4+y (y∼0.06). Nonequilibrium heating was found to occur on a picosecond time scale. The time scale of the nonequilibrium heating is a sensitive measurement of the modest electron‐phonon interaction (λ≤0.1) in the nonsuperconducting La2CuO4+y.
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63.20.K- Phonon interactions
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Laser deposition of epitaxial titanium nitride films on (100) MgO

N. Biunno, J. Narayan, A. R. Srivatsa, and O. W. Holland

Appl. Phys. Lett. 55, 405 (1989); http://dx.doi.org/10.1063/1.101881 (3 pages) | Cited 17 times

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We have investigated the formation of epitaxial (100) oriented TiN films grown on (100) MgO substrates using an excimer laser (wavelength 308 nm, pulse duration 45 ns, and energy density (5–6 J cm−2) physical vapor deposition method. The films were deposited by laser ablation of a TiN target pellet in high vacuum (∼3.0×10−7 Torr), with the substrate temperature ranging from 450 to 750 °C. The epitaxial films were obtained at relatively low substrate temperatures (∼450 °C). The deposited films were analyzed using cross‐section and plan‐view transmission electron microscopy, x‐ray diffraction, Rutherford backscattering/channeling, Auger electron spectroscopy, and electron channeling patterns. The results indicate epitaxial film growth (〈100〉 TiN parallel to 〈100〉MgO) near the stoichiometric TiN composition, and low oxygen content. The minimum channeling yield χmin was found to be ≤10%. The room‐temperature resistivity was as low as 50 μΩ cm and the lattice parameter was found to be 4.218 Å.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification

Detection of water‐related charge in electronic dielectrics

N. Lifshitz and G. Smolinsky

Appl. Phys. Lett. 55, 408 (1989); http://dx.doi.org/10.1063/1.101570 (3 pages) | Cited 4 times

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We observed an unusual behavior of low‐temperature silicon dioxide based materials in the metal‐oxide‐semiconductor system. We used the triangular voltage sweep (TVS) technique to detect the motion of mobile charge in the dielectrics. The observed TVS spectra were different from those usually attributed to common contaminants in silicon dioxides, such as sodium. We came to the conclusion that these unusual TVS traces are due to the motion of protons formed through the electrical decomposition of water absorbed in these materials. The unique features of the water‐related TVS traces may provide a method for detection of water‐related instability in electronic dielectrics.
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77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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Erratum: Heteroepitaxial growth and characterization of GaAs on silicon‐on‐sapphire and sapphire substrates [Appl. Phys. Lett. 54, 1687 (1989)]

J. B. Posthill

Appl. Phys. Lett. 55, 411 (1989); http://dx.doi.org/10.1063/1.102375 (1 page)

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Abstract Unavailable
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.60.Bs Mechanical and acoustical properties
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.61.Ey III-V semiconductors
99.10.Cd Errata
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