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  • 1
    Electronic Resource
    Electronic Resource
    Thin film reaction kinetics of niobium/aluminum multilayers (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1341-1349 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phase formation kinetics in Nb/Al multilayered thin films having overall compositions of 25, 33, 50, and 75 at. % Al have been investigated using scanning calorimetry, x-ray diffraction, and cross-sectional transmission electron microscopy. The first phase to form upon annealing the Nb/Al layered structure of all samples is the NbAl3 intermetallic. Calorimetry clearly identifies the NbAl3 formation to be a two-stage process. The first stage is the formation of a planar layer by nucleation and growth to coalescence while the second stage is the thickening of the planar layer. The large amount of heat released (and hence large volume fraction of NbAl3 formed) during the first reaction stage is consistent with heterogeneous nucleation at well-isolated sites in the Nb/Al interface. This is surprising in light of the large thermodynamic driving force expected for nucleation and suggests that the local nonequilibrium nature of the Nb/Al interface greatly reduces the driving force for nucleation. The next phase observed in samples of 25 and 33 at. % Al is the A15 superconducting phase, Nb3Al. The Nb3Al growth completes a first reaction stage similar to the NbAl3, but the subsequent thickening reaction stage is not observed without simultaneous Nb2Al growth. The high interface velocities derived from the calorimetry for formation of both NbAl3 and the A15 Nb3Al indicate that atomic transport must be by grain boundary diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351744
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  • 2
    Electronic Resource
    Electronic Resource
    Geometry dependence of nonlinear effects in high temperature superconducting transmission lines at microwave frequencies (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1020-1027 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the nature of low-power nonlinear effects in high-temperature superconducting microwave devices by measuring third harmonic generation at 76 K in coplanar waveguide transmission lines of different geometries fabricated from YBa2Cu3O7−δ thin films. The measured power in the third-harmonic signal changes systematically with film thickness, center conductor linewidth, and line length. We analyze these results using a simple model for a transmission line with a nonlinear inductance arising from a current-dependent superconducting penetration depth. This analysis describes quantitatively the observed differences in harmonic generation for transmission lines of different dimensions, and yields a single geometry-independent parameter (the nonlinear scaling current density J0) to quantify the observed nonlinear behavior. For the thin film samples studied here J0=3.0×107 A/cm2 at 76 K for all geometries investigated. These results provide the means to establish a lower limit for the expected nonlinear response of superconducting components of arbitrary geometry at microwave frequencies. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370841
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  • 3
    Electronic Resource
    Electronic Resource
    Hindered ligand systems. VIII. Syntheses of the iron(III), cobalt(III), and nickel(II) compounds of cis,cis-1,3,5-tris(salicylaldimino)cyclohexane and the crystal and molecular structure of the cobalt(III) complex (1975)
    s.l. : American Chemical Society
    Inorganic chemistry 14 (1975), S. 747-751 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic50146a009
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  • 4
    Electronic Resource
    Electronic Resource
    A novel multilayer circuit process using YBa2Cu3Ox/SrTiO3 thin films patterned by wet etching and ion milling (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2752-2754 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A process combining hydrofluoric acid (HF) and Ar+ ion milling has been used to make YBa2Cu3Ox/SrTiO3/YBa2Cu3Ox(YBCO/STO/YBCO) multilayer test circuits. Low-angle steps can be readily etched in STO and YBCO films with this process. YBCO lines crossing 5° steps have about the same critical temperature Tc (89–90 K) and critical current density Jc ((approximately-greater-than)1×106 A/cm2 at 86 K) as lines on planar surfaces. Via connections have the same Tc as other circuit components and adequate critical currents for most circuit designs. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117700
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  • 5
    Electronic Resource
    Electronic Resource
    Noise and dc characteristics of thin-film Bi-Sr-Ca-Cu-oxide dc SQUIDs (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1493-1495 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Highly oriented Bi-Sr-Ca-Cu-oxide thin films with Tc≥100 K and large (10–20 μm) grains were used to produce thin-film dc superconducting quantum interference devices (SQUIDs). The best SQUID, which operated up to 75 K, had an inside loop diameter of ∼18 μm and an estimated loop inductance of 30 pH. The device was patterned by standard photolithography and had weak links that were likely due to existing grain boundaries around the loop. The effective loop area, calculated from the period of the SQUID modulation, is roughly consistent with the geometrical area of the SQUID loop. Significant hysteresis was observed in the flux-voltage characteristic which depended on the amplitude of the magnetic field sweep. The 1/f noise levels measured at 100 Hz in this device gave a flux noise Sφ of 1.0×10−8 Φ20/Hz at 4.8 K and 2.3×10−7 Φ20/Hz at 60 K. The detailed noise measurements which we report for this SQUID are the first for any Bi-Sr-Ca-Cu-oxide based SQUID.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103157
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of Bi-Pb-Sr-Ca-Cu oxide/Ag superconductors by melt dipping and oxidation of metallic precursor alloys (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2227-2229 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi-Pb-Sr-Ca-Cu-Ag alloy coatings were made by vacuum induction melting followed by melt dipping on substrates of MgO, SrTiO3, and Al2O3. The metallic precursor layers were then subjected to a controlled atmosphere oxidation and annealing to produce oxide superconductors. Superconducting coatings with onset temperatures of 112 K and zero resistance temperatures of 80 K were obtained in this way. The addition of Ag aided in the alloy melting and dipping processes, and produced a superconducting oxide/noble metal composite after oxidation. The resulting superconducting phases were analyzed by x-ray powder diffraction. The influence of the substrate, dipping processes, oxidation, and annealing conditions on the superconducting properties are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102353
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  • 7
    Electronic Resource
    Electronic Resource
    Experimental evidence for nucleation during thin-film reactions (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 852-854 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reaction between solid layers to form a product phase has been studied using scanning calorimetry of multilayer Nb/Al and Ni/amorphous-Si thin films. The most striking feature for both materials systems is the occurrence of two maxima in the reaction rate during the formation of a single product phase, suggesting a two step growth process. A model has been developed in which the first step is taken to be the nucleation and two-dimensional growth to coalescence of the product phase, in the plane of the initial interface. The second step is taken to be the thickening of the product layer by growth perpendicular to the interface plane. The success of this simple model in describing the principal features of the experimental results on two different materials systems suggests that nucleation is an important aspect of phase formation and selection in these thin-film reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102447
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  • 8
    Electronic Resource
    Electronic Resource
    Preparation of superconducting thin films of bismuth strontium calcium copper oxides by reactive sputtering (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 246-248 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting thin films of Bi-Sr-Ca-Cu-oxides have been reproducibly prepared by reactive magnetically enhanced triode sputtering using three separate metal targets (Sr, Ca, and Cu-Bi). Oxygen was introduced directly at the substrates during film growth. The films were deposited on ambient temperature substrates [Al2O3, SrTiO3, and yttria-stabilized zirconia (YSZ)] and had thicknesses of 0.5–1.5 μm. After deposition, the films were annealed at 850–900 °C in flowing oxygen. The electrical resistance of the best films on YSZ decreased approximately linearly with temperature until the onset of superconductivity at about 85 K. Zero resistance was achieved by 74 K. Critical current densities in excess of 5×105 A/cm2 at 4.2 K were also obtained. X-ray diffraction demonstrated that the best films were nearly single phase (Bi2Sr2Ca1Cu2O8+x) and textured with the c axis perpendicular to the substrate. The effect of composition and annealing on our results is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100589
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  • 9
    Electronic Resource
    Electronic Resource
    Insulating nanoparticles on YBa2Cu3O7−δ thin films revealed by comparison of atomic force and scanning tunneling microscopy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 614-616 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface topography of YBa2Cu3O7−δ thin films has been studied with both atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The AFM images reveal a high density of small distinct nanoparticles, 10–50 nm across and 5–20 nm high, which do not appear in STM images of the same samples. In addition, we have shown that scanning the STM tip across the surface breaks off these particles and moves them to the edge of the scanned area, where they can later be imaged with the AFM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109966
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  • 10
    Electronic Resource
    Electronic Resource
    Antenna-coupled high-Tc air-bridge microbolometer on silicon (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 773-775 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An antenna-coupled high-Tc superconducting microbolometer on a silicon substrate, operating at infrared wavelengths, is described. This detector incorporates a silicon-micromachined yttria-stabilized zirconia air bridge at the feed of a planar lithographic antenna to simultaneously minimize the thermal conductance and the heat capacity of the bolometer. At an operating temperature of 87.4 K, the optical responsivity measured using a 300-K blackbody source over a 0.2–2.9 THz bandwidth is 2900 V/W, the optical noise-equivalent power (NEP) is 9×10−12 W/Hz1/2, and the time constant is 〈10 μs. This NEP is nearly a factor of 2 lower than the previous record for a liquid-nitrogen-cooled thermal detector, and the time constant is several orders of magnitude shorter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112226
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