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  • 1
    Electronic Resource
    Electronic Resource
    Optimization of annealing temperature for YBa2Cu3O7 thin films post-annealed at a low oxygen partial pressure (1991)
    Springer
    Journal of superconductivity 4 (1991), S. 279-282 
    Details
    ISSN: 1572-9605
    Keywords: Superconducting films ; YBa2Cu3O7 ; annealing temperature ; LaAlO3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Post-annealing of YBa2Cu3O7 (YBCO) thin films is usually performed at 850–900°C in atmospheric-pressure oxygen. In this study, coevaporated YBCO films on LaAlO3 were post-annealed in an oxygen partial pressure of 29 Pa at temperatures in the range 700–825°C. Zero resistance transition temperatures were 89–90 K. Both d.c. (room-temperature resistance and critical-current density) and a.c. parameters (extracted from eddy-current response measurements at 25 MHz) were monitored. The optimum temperature is close to 750°C, which is on the YBCO thermodynamic stability line at this low oxygen partial pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618149
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Film thickness dependence of critical current density for YBa2Cu3O7 films post-annealed at a low oxygen partial pressure (1993)
    Springer
    Journal of superconductivity 6 (1993), S. 37-41 
    Details
    ISSN: 1572-9605
    Keywords: Superconducting films ; YBa2Cu3O7 ; critical current density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The variation of critical current density at 77 K as a function of film thickness was studied for YBa2Cu3O7 films on (100) LaAlO3 substrates. Film thicknesses were in the range 0.2–1.6μm. The films were deposited by co-evaporation and post-annealed under conditions which have previously resulted in high-quality films (750°C and an oxygen partial pressure of 29 Pa). The critical current density at 77 K exceeds 1 MA cm−2 for the thinner films, and decreases with increasing film thickness in excess of about 0.4μm. The decrease is in rough agreement with a switch fromc-axis toa-axis growth at about this critical thickness. A good anticorrelation was found between room temperature resistivity and critical current density at 77 K. The results are compared to those obtained before by post-annealing at 850°C in 1 atm of oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618503
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Reproducibility of transition temperature and critical current density of thin films of YBa2Cu3O7 on (100) LaAlO3 (1991)
    Springer
    Journal of superconductivity 4 (1991), S. 61-65 
    Details
    ISSN: 1572-9605
    Keywords: Superconducting films ; YBa2Cu3O7 ; critical current ; LaAlO3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Submicrometer epitaxial films of YBa2Cu3O7(YBCO) on (100) LaAlO3 were made by coevaporation and furnace annealing. Samples from more than a dozen runs are used in this study. The zero resistance transition temperature (T c) is high (89 or 90 K) if the film composition is phase pure (Ba/Y=2, Cu/Y=3) or if it is enriched in Ba and Cu. For these compositions the critical current density (J c) at 77 K has an average value of 2×105 A cm−2, with a tendency for decreasingJ c with increasing film thickness (0.2 to 0.8μm). Variations inJ c are not correlated with deviations from ideal stoichiometry. Steeper slopes of the resistance-temperature curves above 100 K and lower values of the room-temperature resistivity are associated with high values ofJ c. If the film composition is enriched in Y relative to Ba and Cu,T c decreases by several degrees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618299
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Critical current density and microstructure of YBa2Cu3O7 thin films post-annealed at a low oxygen partial pressure (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 143-147 
    Details
    ISSN: 1572-9605
    Keywords: Superconducting films ; YBa2Cu3O7 ; critical current density ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Post-annealing of thin films of YBa2Cu3O7 (YBCO) has been performed at 29 Pa and 750°C. For films 0.6 μm thick, a critical current density 〉1 MA cm−2 is obtained at 77 K, with a sharp eddy current response at 25 MHz. Microstructural investigation of these films by crosssectional and planar transmission electron microscopy reveals that the YBCO film has thec-axis normal to the plane of the substrate in a continuous sheet of varying thickness, frequently covering the entire thickness of the film. Mutually perpendicular rods with thec-axis in the plane of the LaAlO3 substrate are also seen. The microstructure and critical current density of these films are compared with those of previously reported films post-annealed in atmosphericpressure oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618058
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Process monitoring during post-annealing of YBa2Cu3O7 thin films containing fluorine (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 167-170 
    Details
    ISSN: 1572-9605
    Keywords: Superconducting films ; YBa2Cu3O7 ; post-annealing ; process monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The post-annealing method of producing thin films of YBa2Cu3O7 (YBCO) has taken on a new impetus due to the recent work showing that films of the highest quality can be made by using low partial pressures of oxygen during the annealing cycle. Here it is shown that for films produced by using BaF2 as a source material, the post-annealing procedure can be closely controlled by monitoring the F that evolves due to the water vapor reaction with BaF2. The use of an ion-sensitive electrode allowed small F evolution rates (about 1 ng s−1) to be detected above background, sufficient to measure the F evolution rate from even the smallest samples used. The time interval during which F evolves was found to increase with increasing YBCO film area being annealed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618062
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Degradation of thin films of YBa2Cu3O7 by annealing in air and in vacuum (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 95-98 
    Details
    ISSN: 1572-9605
    Keywords: Superconducting films ; YBa2Cu3O7 ; degradation of superconducting properties ; critical current density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The degradation of epitaxial thin films of YBa2Cu3O7 has been studied as a function of annealing temperature in air and in vacuum; some samples had an evaporated overlayer of CaF2. Degradation was monitored by the measurement of electrical properties after consecutive 30-min annealing treatments. The room-temperature resistance registered significant increases for all samples after annealing at temperatures above about 200°C; the critical current density at 77 K was degraded for annealing temperatures ≥400°C in air, and ≥200–250°C in vacuum. By annealing in oxygen at 550°C, electrical properties were restored in degraded bare YBCO samples annealed in vacuum, but not for those annealed in air.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732247
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    Paper (German National Licenses)
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