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1 Aug 1988

Volume 53, Issue 5, pp. 347-452

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Dependence of Tc on hole concentration in the superconductors Bi4Sr3Ca3−xYxCu4O16+δ

A. Manthiram and J. B. Goodenough

Appl. Phys. Lett. 53, 420 (1988); http://dx.doi.org/10.1063/1.100608 (3 pages) | Cited 53 times

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Substitution of Y for Ca in the high Tc superconductor system Bi4Sr3Ca3−xYxCu4O16+δ (0≤x≤1.5) is accompanied by an increase in oxygen concentration δ≊0.34+0.3x that is insufficient to compensate for the increase in counter‐cation valence. Nevertheless, Tc≊86 K remains nearly constant in the interval 0≤x≤0.5; it drops smoothly to zero in the interval 0.5<x≤1.15. Correlation of the compositional limit x=0.5 of the Tc plateau with the onset of trapping of holes could indicate that any oxygen atom in excess of O16.5 occupies a different crystallographic position where it traps two holes either as Bi5+ or as (O2)2−.
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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
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Preparation of Bi‐Sr‐Ca‐Cu‐O superconductors from oxide‐glass precursors

D. G. Hinks, L. Soderholm, D. W. Capone, B. Dabrowski, A. W. Mitchell, and D. Shi

Appl. Phys. Lett. 53, 423 (1988); http://dx.doi.org/10.1063/1.100609 (3 pages) | Cited 61 times

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In this letter we report on efforts to synthesize the new Ca‐Sr‐Bi‐Cu‐O superconductors from amorphous glasses. These glasses are produced by quenching melts of the constituent oxides, followed by firing to produce the superconducting phase. This synthetic route produces denser, more uniform samples than those obtained from firing intimate mixtures of the constituent binary oxides and carbonates. Ultimately, this technique may yield pure materials with enhanced bulk properties.
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81.05.Kf Glasses (including metallic glasses)
74.70.-b Superconducting materials other than cuprates
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Two‐dimensional superstructure in the (001) plane of Bi2[Ca,Sr]3Cu2O8+δ thin films

A. F. Marshall, B. Oh, S. Spielman, Mark Lee, C. B. Eom, R. W. Barton, R. H. Hammond, A. Kapitulnik, M. R. Beasley, and T. H. Geballe

Appl. Phys. Lett. 53, 426 (1988); http://dx.doi.org/10.1063/1.100610 (3 pages) | Cited 18 times

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Thin films of Bi‐Ca‐Sr‐Cu‐O showing superconductivity above 100 K have been made by electron beam evaporation with oxygen post‐annealing. The major superconducting phase, Bi2[Ca,Sr]3Cu2O8+δ (Tc ∼85 K), is oriented epitaxially with the (100)SrTiO3 substrate. In addition to the one‐dimensional incommensurate superstructure along the b axis, which is characteristic of this phase, we have observed by transmission electron microscopy a two‐dimensional incommensurate superstructure in the a‐b plane with a different periodicity and a different orientation relationship to the subcell.
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74.70.-b Superconducting materials other than cuprates
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures

Growth and microstructure of Bi‐Sr‐Ca‐Cu‐O thin films

S. I. Shah and G. A. Jones

Appl. Phys. Lett. 53, 429 (1988); http://dx.doi.org/10.1063/1.100671 (3 pages) | Cited 11 times

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Thin superconducting Bi‐Sr‐Ca‐Cu‐O films have been grown by reactive magnetron sputtering with an average cation ratio of 2:2:1:2 on single‐crystal (100)MgO. Films show a superconducting transition onset at 117 K, but do not go to zero resistance until 83–84 K. Secondary electron microscopy and electron beam microprobe showed two major phases with different compositions and morphologies. The dominant phase was a lamellar phase with composition very close to the 2:2:1:2 cation ratio. The second phase had a needle‐like morphology, which was deficient in Bi, and had excess Cu. The nonsuperconducting Sr14−xCaxCu24O41 phase had been known to exist in bulk; therefore, the needle phase could be an intermediate step in the formation of Sr14−xCaxCu24O41 phase as Bi deficiency in the needles increased with increasing annealing temperature and/or time.
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81.15.Cd Deposition by sputtering
74.70.-b Superconducting materials other than cuprates
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Crystallography and microstructure of Tl‐Ca‐Ba‐Cu‐O superconducting oxides

R. Beyers, S. S. P. Parkin, V. Y. Lee, A. I. Nazzal, R. Savoy, G. Gorman, T. C. Huang, and S. La Placa

Appl. Phys. Lett. 53, 432 (1988); http://dx.doi.org/10.1063/1.100611 (3 pages) | Cited 43 times

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We report on the crystallography and microstructure of six oxides in the Tl‐Ca‐Ba‐Cu‐O system with nominal compositions Tl1Ba2Cu1O5, Tl1Ca1Ba2Cu2O7, Tl1Ca2Ba2Cu3O9, Tl2Ba2Cu1O6, Tl2Ca1Ba2Cu2O8, and Tl2Ca2Ba2Cu3O10. The structures consist of one, two, or three Cu perovskite‐like units sandwiched between Tl‐O monolayers or bilayers. The predominant defects in the crystals with bilayer and trilayer Cu perovskite‐like units are stacking faults that produce local intergrowths of related structures. The density of stacking defects in these oxides correlates with changes in the superconducting transition temperatures.
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74.70.-b Superconducting materials other than cuprates
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations

Grain growth of rapid‐thermal‐annealed Y‐Ba‐Cu oxide superconducting thin films

A. H. Hamdi, J. V. Mantese, A. L. Micheli, R. A. Waldo, Y. L. Chen, and C. A. Wong

Appl. Phys. Lett. 53, 435 (1988); http://dx.doi.org/10.1063/1.100612 (3 pages) | Cited 5 times

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A study of the microstructure of Cu‐rich and stoichiometric Y‐Ba‐Cu oxide thin‐film superconductors is presented. The films were deposited on 〈100〉 SrTiO3 by the nonvacuum technique of metalorganic deposition followed by rapid thermal annealing in oxygen. Analysis showed that for annealing temperatures below 900 °C, grain size increased with increased annealing temperature, with an enhancement in grain growth for the Cu‐rich films. Annealing near or above the melting point of the 1‐2‐3 phase causes only a slight increase in the rate of grain growth and no detectable effects of the excess Cu. Annealing above 920 °C produces segregated CuO islands 5–10 μm in size in the Cu‐rich films. Oriented grain growth was found for the 1‐2‐3 grains with their c axis perpendicular and parallel to the SrTiO3 substrates. Sheet resistivity measurements were correlated with grain size, phase separation, and oriented grain growth. An anomalous behavior in the resistance‐temperature plot at 220–240 K of the Cu‐rich films is shown to be related to the presence of the excess Cu.
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74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Superconducting yttrium‐barium‐copper‐oxide ribbons fabricated from a metal alloy precursor

F. E. Pinkerton, G. P. Meisner, and C. D. Fuerst

Appl. Phys. Lett. 53, 438 (1988); http://dx.doi.org/10.1063/1.100613 (3 pages) | Cited 1 time

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We report a new process for making superconducting Y‐Ba‐Cu‐oxide ribbon from a ductile metal alloy precursor ribbon. We begin by melt‐spinnng an alloy having the composition YCu3 to obtain the microcrystalline precursor ribbon. The ribbon is coated with a molten mixture of Ba inorganic compounds at 550 °C, and reacted in air at 925 °C to form the superconducting YBa2Cu3O7−x phase. The superconducting onset occurs at 92 K and zero resistance is reached at 89 K. X‐ray diffraction, electron microscopy, and magnetization measurements confirm that the ribbon is predominantly superconducting YBa2Cu3O7−x.
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81.05.Bx Metals, semimetals, and alloys
74.70.-b Superconducting materials other than cuprates
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
61.05.cp X-ray diffraction

Parameters for in situ growth of high Tc superconducting thin films using an oxygen plasma source

R. J. Spah, H. F. Hess, H. L. Stormer, A. E. White, and K. T. Short

Appl. Phys. Lett. 53, 441 (1988); http://dx.doi.org/10.1063/1.100614 (3 pages) | Cited 19 times

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Superconducting thin films of Dy‐Ba‐Cu‐O have been grown on 3 in. sapphire wafers with a molecular beam deposition process. Dissociated oxygen from a glow discharge source was used to improve the oxygen incorporation. This allows growth on a relatively low‐temperature substrate kept below 600 °C followed by an in situ anneal below 400 °C. Thin films of Dy‐Ba‐Cu‐O which were fully superconducting at 40 K have been fabricated by this in situ growth process.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Reliable single‐target sputtering process for high‐temperature superconducting films and devices

R. L. Sandstrom, W. J. Gallagher, T. R. Dinger, R. H. Koch, R. B. Laibowitz, A. W. Kleinsasser, R. J. Gambino, B. Bumble, and M. F. Chisholm

Appl. Phys. Lett. 53, 444 (1988); http://dx.doi.org/10.1063/1.100615 (3 pages) | Cited 55 times

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We report a simple, single‐target magnetron sputtering process for films of high‐temperature superconductors involving an off‐axis sputtering geometry. The process lends itself both to film growth with high‐temperature post‐anneals and to low‐temperature in situ film growth. The post‐anneal process routinely yields YBa2Cu3O7−x films on SrTiO3 substrates that are fully superconducting at 86–89 K. Current densities at 77 K range from 104 to 8×105 A/cm2. A single‐level superconducting quantum interference device (dc SQUID), made by photolithographically patterning a low current density film, has a flux noise level at 77 K of 3×10−4 Φ0/(Hz)1/2 at 20 Hz, dominated by low‐frequency noise associated with flux motion in the film.
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74.70.-b Superconducting materials other than cuprates
81.15.Cd Deposition by sputtering
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.78.-w Superconducting films and low-dimensional structures

Antiferromagnetic spin waves in superlattices of diluted magnetic semiconductors

Murielle Villeret, S. Rodriguez, and E. Kartheuser

Appl. Phys. Lett. 53, 447 (1988); http://dx.doi.org/10.1063/1.99894 (3 pages) | Cited 2 times

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We present an analysis of the long‐wavelength spin‐wave excitations in superlattices of diluted magnetic semiconductors. The different magnetic modes are classified as ‘‘pure‐bulk,’’ ‘‘pure‐interface,’’ and ‘‘bulk‐interface’’ depending on whether they propagate along the axis of the superlattice in the two components of the structure, they decay in both regions, or they propagate in one and decay in the other. Numerical applications are considered related to inelastic light scattering from superlattices of Cd1−xMnxTe.
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75.30.Ds Spin waves
75.50.Pp Magnetic semiconductors
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Zn1−xCoxSe: A new diluted magnetic semiconductor grown by molecular beam epitaxy

B. T. Jonker, J. J. Krebs, and G. A. Prinz

Appl. Phys. Lett. 53, 450 (1988); http://dx.doi.org/10.1063/1.99895 (3 pages) | Cited 17 times

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We have grown single‐crystal epilayers of the new diluted magnetic semiconductor Zn1−xCox Se on GaAs(001) substrates by molecular beam epitaxy. X‐ray θ‐2θ and double‐crystal rocking curve measurements were used to obtain the variation in lattice parameter and evaluate crystalline quality. Temperature‐dependent electron paramagnetic resonance and superconducting quantum interference device magnetometry data confirm the substitutional nature of the Co2+ in the zinc site and paramagnetic behavior.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
75.50.Pp Magnetic semiconductors
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