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  • Oxford University Press  (40)
  • American Institute of Physics (AIP)  (10)
  • Geological Society of America (GSA)
  • 1
    Digitale Medien
    Digitale Medien
    Resolution limits of ion milling for fabricating Y1Ba2Cu3Ox nanostructures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2461-2463 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A process is described for fabricating 0.23-μm-wide lines in Y1Ba2Cu3Ox thin films where patterns are defined in a commercial, negative tone, epoxy-based resist by masked ion beam lithography and transferred to the superconducting film by argon ion milling. Lines in 80-nm-thick films had the same zero-resistance temperature (89 K) as the starting films, and a critical current density of 0.7×106 A/cm2 at 77 K, representing a threefold reduction from the starting value. A consistent interpretation of these results is that the line consists of a superconducting core 70 nm in width with the critical current density of the starting film and with 80-nm-wide nonsuperconducting sidewalls. The results were reproducible in lines which did not cross outgrowths in the superconducting film.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351112
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  • 2
    Digitale Medien
    Digitale Medien
    Deposition of high quality YBa2Cu3O7−δ thin films over large areas by pulsed laser ablation with substrate scanning (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7182-7188 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We describe the transport and structural properties of YBa2Cu3O7−δ thin films deposited by pulsed laser ablation with computer-controlled substrate scanning. Films were deposited on LaAlO3 and SrTiO3 substrates covering a 2×3 cm area with thicknesses of 90 and 160 nm. The 90-nm thick films exhibited a thickness variation of ±8%, Tco = 90.7 ± 0.5 K, Jc = 4.8 ± 0.2 × 106 A/cm2 at 77 K, and a surface resistance (corrected for finite thickness) at 75 GHz of 10–12 mΩ at 77 K. For the 160-nm thick films, the thickness variation was 〈5%, Tco = 91.0 ± 0.3 K, Jc=5.4±0.4×106 A/cm2, and corrected surface resistance was 6–10 mΩ. X-ray diffraction showed that the c-axis mosaic in the films is closely related to that of the substrates and that the only in-plane defects are due to the expected twinning in the a-b plane of the film. The c-axis lattice constants were 1.1688±0.0004 nm. The above properties showed a high degree of uniformity across the substrate area and between films from different deposition cycles. The surface resistance values add significantly to the body of results which show that the temperature-scaled values for niobium can be equaled and perhaps surpassed by YBa2Cu3O7−δ.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347611
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  • 3
    Digitale Medien
    Digitale Medien
    Superconductivity in the Bi-Sr-Ca-Cu-O compounds with noble metal additions (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1628-1630 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The Bi-Sr-Ca-Cu-O superconductors have been doped with various noble metals and their superconducting properties have been investigated. The resistivity and magnetic susceptibility measurements on sintered Bi4Sr3Ca2Cu4O16+x containing 20% by weight of Au, Ag, or Pt-group metals indicate that Au and the Pt-group metals significantly suppress or eliminate the superconducting transition in Bi-Sr-Ca-Cu-O. Only Ag is found to be benign, maintaining both the 115 and 85 K transitions in the compound. This nonpoisoning behavior of silver is of significant technical importance because of the need for a proper stabilizing normal metal for composite superconductor wire, nonreactive crucible materials for melt processing or crystal growth, and suitable nonpoisonous substrates or barriers for thin- or thick-film superconducting devices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99705
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  • 4
    Digitale Medien
    Digitale Medien
    High critical currents in Y-Ba-Cu-O superconductors (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 2074-2076 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Melt-textured growth of polycrystalline YBa2Cu3O7−δ superconductor using directional solidification created an essentially 100% dense structure consisting of long, needle- or plate-shaped crystals preferentially aligned parallel to the a-b conduction plane. The new microstructure, which completely replaces the previous granular and random structure in the sintered precursor, exhibits dramatically improved transport Jc values at 77 K of ∼17 000 A/cm2 in zero field and ∼4000 A/cm2 at H=1 T (as compared to ∼500 and ∼1 A/cm2, respectively, for the as-sintered structure), with the severe field dependence of Jc ("weak-link'' problem) no longer evident in the new melt-textured material. The improvement in Jc is attributed to the combined effects of densification, alignment of crystals, and formation of cleaner grain boundaries. Microstructure and distribution of various phases present in the melt-textured material are discussed in relation to the superconducting properties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99751
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  • 5
    Digitale Medien
    Digitale Medien
    Low-resistivity contacts to bulk high Tc superconductors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2605-2607 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Convenient methods for obtaining extremely low resistivity contacts to bulk high Tc superconductors ( ρc in the range of 10−11–10−12 Ω cm2) are described. Three different configurations of silver contact metal in Y-Ba-Cu-O have been employed, i.e., embedded Ag wire, embedded Ag particles, and selectively patterned Ag clad on superconductor wire. In all three cases, the low-resistivity metallic contacts are formed in situ during the sintering or melt processing of the superconductor, thus eliminating the need for separate steps of contact preparation such as vacuum deposition of contact metal and additional heat treatment. The distribution and morphology of the silver contacts will be discussed. The measured contact resistivities in the present work are the lowest reported for the high Tc superconductors, and these methods may serve as a useful basis for important contact technologies needed for bulk superconductor applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101038
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  • 6
    Digitale Medien
    Digitale Medien
    Large magnetic hysteresis in a melt-textured Y-Ba-Cu-O superconductor (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 584-586 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Melt-textured YBa2Cu3O7−δ superconductor with a long and well-aligned grain structure is shown to exhibit magnetic hysteresis at 77 K which is the largest ever reported for bulk polycrystalline Y-Ba-Cu-O. The large ΔM resulted in a magnet-like behavior as well as a strong suspension phenomenon. It is shown, contrary to the previous reports, that the suspension behavior observed in Y-Ba-Cu-O is a generic consequence of large grain size, and not due to the presence of Ag oxide or Ag particles. There appears to be no substantial enhancement in flux pinning and Jc by these particles. Comparisons of magnetization behavior in various YBa2Cu3O7−δ samples (polycrystals, silver-oxide doped, melt-textured, and single crystals) indicated that for applied fields substantially larger than Hc1 the current flow that gives rise to the observed magnetization is intragranular. The pinning force and hence the critical current is roughly the same [Jc (magn)∼104 A/cm2] within a factor of ∼2 regardless of grain size, grain boundary configuration, presence of second phase particles, or increased dislocation and twin densities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101464
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  • 7
    Digitale Medien
    Digitale Medien
    Fabrication and properties of high-Tc superconducting wires (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5896-5898 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The discovery of high-temperature superconductivity in perovskite-related oxides has generated an enormous amount of research activity and development effort toward applications. Commercially useful bulk superconductors typically require stabilization using a normal metal cladding for reasons of electrical, thermal, and mechanical protection, and in general need to be fabricated into fine fibers and wound into a solenoid configuration. The YBa2Cu3O7−δ type compound is a ceramic material which is mechanically hard and brittle, and is difficult to fabricate into fine wires. However, this difficulty has been overcome by several fabrication methods such as powder-in-tube method (metal-clad composite), powder-coating method (metal-core composite), and molten oxide processing method. The effect of various processing steps on the structure and superconducting properties such as transition temperature and critical current density will be discussed. Some experiments to raise the high field critical current through chemistry and microstructural control will also be described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.342194
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  • 8
    Digitale Medien
    Digitale Medien
    Bi-Sr-Ca-Cu-O high TC superconductors (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5815-5815 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A recent paper by Maeda et al.1 reported the discovery of a new 120 K superconductor based on a rare-earth–free ceramic material in the bismuth-strontium-calcium-copper-oxide system. We have confirmed the existence of the 120-K phase in the oxide system. The resistivity-temperature curve showed a fairly well-defined double-dip shape with the first dip starting at ∼120 K and the second at ∼95 K. The transition temperature, TC(R=0), was 84 K. This material appears to contain two superconducting phases with different TC's. A pellet made from this superconductor levitates well at 77 K (liquid-nitrogen temperature) above a neodynium-iron-boron magnet with a surface magnetic field of ∼3000 Oe, thus indicating a nontrivial critical field in this material. The critical current density and its magnetic field dependence will be reported. The magnetic and mechanical behavior of the new superconductor will also be discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.342214
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  • 9
    Digitale Medien
    Digitale Medien
    Doping of p-type shallow junctions using electron beam evaporation of boron layers for compatibility with complementary-metal-oxide-semiconductor technology (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 76-78 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electron-beam evaporation was used as a low-temperature deposition process of boron and boron/amorphous-silicon layers as dopant sources in rapid thermal diffusion. High efficiency of doping is attributed to high dopant supply from the boron layer to the silicon substrate. Oxygen ambient leads to layer consumption and thus opens possibility for the source removal after diffusion. Dopant activation results in high carrier concentration within the junctions. High concentrations of dopant cause generation of precipitates at the B/Si substrate interface but not at the B/Si cap interface. The process is compatible with the complementary-metal-oxide-semiconductor technology since the low temperature of the source deposition facilitates masking of the dopant by a patterned photoresist and its subsequent lift-off removal from the silicon surface. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.114150
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  • 10
    Digitale Medien
    Digitale Medien
    Linewidth dependence of critical current density in Y1Ba2Cu3O7 thin-film microbridges (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1129-1131 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A study of the dependence of the transport critical current density (Jc) on the width of Y1Ba2Cu3O7 thin-film microbridges with widths down to 2 μm has been made. No evidence of edge pinning, which leads to larger Jc's in narrower microbridges, was found. Due to the limitation in resolution of photolithography encountered in common usage, a tapered or radiation damaged edge was always present, which may have introduced a significant error in the cross section and hence in the estimation of Jc. By normalizing the critical current (Ic) to the room-temperature resistance of the microbridge, we can eliminate this mask-defined cross-sectional error.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.106366
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