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  • 1
    Electronic Resource
    Electronic Resource
    Superconducting and structural properties of Nd2−xCexCuO4−y thin films on perovskite and fluorite substrates (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2119-2124 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality epitaxial Nd2−xCexCuO4−y (NCCO) thin films were fabricated on various substrates by pulsed-laser deposition using N2O reactive gas. The similarities and dissimilarities of the superconducting and structural properties of NCCO films, on perovskite-type substrates such as LaAlO3, NdGaO3, and SrTiO3 and on a fluorite-type substrate of yttria-stabilized zirconia (YSZ), were investigated systematically as a function of film thickness by transport measurements and structural analysis. A remarkable reduction of Tc was observed when the film was thinner than a critical thickness, which strongly depends on the substrate. The critical thicknesses for which Tc is 80% of Tc max are 1200, 1000, 600, and 450 A(ring) for LaAlO3, NdGaO3, SrTiO3, and YSZ, respectively. YSZ turns out to be the best candidate for the growth of very thin NCCO films among the substrates studied. These results show a strong correlation between the strain and Tc in NCCO thin films and point the way to the fabrication of n-type superconducting electric field devices using ultrathin NCCO films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356318
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  • 2
    Electronic Resource
    Electronic Resource
    Transport and magnetism correlations in thin-film ferromagnetic oxides : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4535-4537 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To determine the Tc dependence of the colossal magnetoresistance (CMR) exhibited by the ferromagnetic La0.7A0.3MnO3+δ (A=Ba, Ca, Sr) system, we examine the magnetic-field and temperature-dependent resistivity and magnetization of a series of thin films that were grown via pulsed-laser deposition. The films had magnetic ordering temperatures (Tc) ranging from 150 to 350 K. All samples display a large negative MR that is largest near Tc, and samples with a low Tc display significantly larger MR values than do samples with large Tc's. The quantity ρ(Tc)/ρ(4 K), the amount by which the resistivity is reduced by full ferromagnetic order, varies as exp(Ea/Tc) with an activation energy Ea=0.1 eV. These results indicate that the magnitude of the CMR effect in a given specimen is controlled not by ρ(Tc), but by Tc via the ratio ρ(Tc)/ρ(4 K). Phenomenological scaling relationships are also reported that link ρ(H,T) to both H and M(H,T). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361715
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  • 3
    Electronic Resource
    Electronic Resource
    Superconductor GdBa2Cu3O7−δ edge junctions with lattice-matched Y0.6Pr0.4Ba2Cu3O7−δ barriers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2871-2873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-temperature-superconductor Josephson junctions with an edge geometry of superconductor/normal-metal/superconductor have been fabricated on yttria-stabilized zirconia substrates by engineering the electrode and N-layer material to reduce the lattice mismatches (a, b, and c). With GdBa2Cu3O7−δ as electrodes and Pr-doped Y0.6Pr0.4Ba2Cu3O7−δ as a barrier, the lattice mismatches from electrode and barrier layer are reduced to a very low level. The junctions fabricated with such a design demonstrate resistively shunted junction current-voltage characteristics under dc bias at temperatures in the range of 77–88 K. The quite low specific interface resistivity on the order of 10−10 Ω cm2 indicates that the junction performance is controlled by the normal-metal (N) layer material instead of the interfaces. The use of lattice-matched electrode and N-layer material is one of the key design rules to obtain controllable high-temperature superconductor Josephson junctions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360094
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  • 4
    Electronic Resource
    Electronic Resource
    Rapid laser-induced growth of nitride and oxide layers at a beryllium/liquid interface (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 293-295 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Excimer laser irradiation was used to induce rapid formation of nitride and oxide layers on beryllium samples immersed in liquid nitrogen and water, respectively. The elemental composition of the irradiated surfaces was determined by means of Rutherford backscattering spectrometry. Compound formation of Be3N2 and BeO was confirmed by x-ray diffraction. The results show that extensive reaction occurred only if the laser energy was sufficient to melt the beryllium surface. The amount of incorporated nitrogen or oxygen atoms was initially proportional to the laser energy density and to the number of laser shots. Saturation occurred when a near stoichiometric layer of Be3N2 or BeO was formed at the surface. The rate of compound formation was extremely high, on the order of 10–100 nm per shot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339143
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  • 5
    Electronic Resource
    Electronic Resource
    Surface layers on superconducting Y-Ba-Cu-O films studied with x-ray photoelectron spectroscopy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 7483-7487 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy (XPS) examines only a thin surface layer (〈5 nm) that may not be representative of the bulk. We separated the information from the surface and bulk by using laser-deposited superconducting films that have nearly atomically flat surfaces for which quantitative analysis formalisms exist. The chemical compositions of high Tc (90 K) and high Jc (〉106 A/cm2) Y-Ba-Cu-O films on SrTiO3 (001) substrates were examined. From the relative intensities of the surface and bulk components of the Ba(3d) and Ba(4d) spectra taken at different take-off angles and different escape depths [using Al Kα (1486.6 eV) and Mg Kα (1253.6 eV) excitations], we have determined the nonsuperconducting surface layer thickness to be 1 nm and the layer composition to be BaCuO2. The surface layer thickness for a superconducting film only 8 nm thick was also 1 nm. By detecting the substrate Ti signal through this film, and ruling out a high density pinholes, we provide evidence that the XPS data contain information from the superconducting phase. A polycrystalline pellet scraped in vacuum had a surface layer only 0.4 nm thick. Since typical photoelectron escape depths are about 2 nm, about 80% of the detected signal originates in the bulk. The surface layer contains Cu2+ and oxygen with a photoelectron binding energy of 531 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345834
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  • 6
    Electronic Resource
    Electronic Resource
    Substrate effects on the properties of Y-Ba-Cu-O superconducting films prepared by laser deposition (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4591-4598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting thin films of Y1Ba2Cu3Ox with superconducting transition temperature (Tc) near 90 K have been prepared by a laser deposition technique. We show that films prepared on sapphire, lithium niobate, and strontium titanate under identical processing conditions exhibit different electrical characteristics. The film surfaces, interfaces, and crystallinity have been studied by a number of analytical techniques. We conclude that the substrate influences the film properties primarily in three ways: the thermal expansion mismatch introduces cracks in the film, the interface reaction changes the film composition, and the substrate lattice influences the crystallographic orientation of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340136
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  • 7
    Electronic Resource
    Electronic Resource
    Raman scattering investigation of a single-crystal-like YBa2Cu3O7−y film (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4452-4453 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature Raman spectra from a single-crystal-like film of YBa2Cu3O7−y fabricated by pulsed laser deposition are compared with similar spectra of a single crystal of YBa2Cu3O7−y. The comparison shows that not only is the axis perpendicular to the plane of the film, but that in addition the a-b axes are well oriented in the film plane. The data also show that the film is spatially uniform with respect to this orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343289
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  • 8
    Electronic Resource
    Electronic Resource
    Epitaxial relations between in situ superconducting YBa2Cu3O7−x thin films and BaTiO3/MgAl2O4/Si substrates (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1772-1776 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ superconducting YBa2Cu3O7−x films with Tc0 up to 87 K and Jc, 77 K up to 6×104 A/cm2 were prepared on Si substrates with MgAl2O4 and BaTiO3 double-buffer layers. The epitaxial relations between various layers were established by transmission electron microscopy. The MgAl2O4 layer is heavily faulted. The subsequent BaTiO3 layer stops most of the faults, provides a template for the YBa2Cu3O7−x growth, and partially screens off the stress due to different thermal expansion coefficients. The microstructure of the YBa2Cu3O7−x layer is very similar to that of the films deposited directly on SrTiO3, exhibiting a homogeneous heavily faulted single-crystal-like structure free from secondary phases and grain boundaries. The slight degradation of the transport properties is attributed to residual thermal stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346607
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  • 9
    Electronic Resource
    Electronic Resource
    Correlation of surface topography and flux pinning in superconducting YBaCuO films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5099-5102 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface topography of YBa2Cu3O7 thin films prepared by pulsed laser deposition is studied by atomic force microscopy and scanning tunneling microscopy. The possible contributions from observed structural features to the critical current density Jc are discussed. It is shown that the contribution of the screw dislocations associated with some structures can be either repulsive or attractive, depending on the dominant pinning mechanism. At low magnetic fields (to about 0.25 kOe) these dislocations can account for the observed critical current density values (Jc(approximately-greater-than)1011 A/m2) while for larger fields the higher-density steplike growth structures can account for significant values of Jc. It is shown that the pinning strength associated with pinning at steps varies inversely with thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350612
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  • 10
    Electronic Resource
    Electronic Resource
    Properties of YBa2Cu3O7−δ thick films on flexible buffered metallic substrates (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2397-2399 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report superconducting and mechanical properties of YBa2Cu3O7−δ (YBCO) thick films on Ni-based alloys with a textured yttria-stabilized zirconia (YSZ) buffer layer. The YBCO and YSZ layers were deposited by pulsed laser deposition and ion beam assisted deposition, respectively. It was found that the transport critical current density (Jc) correlates very well with the YBCO mosaic spread. Jc over 1×10 6 A/cm2 at 75 K and ∼1×107 A/cm2 at 4 K were obtained in the 1-μm thick YBCO films. Zero field critical current of 120 amps at 75 K was obtained in a 2-μm-thick and 1-cm-wide YBCO film. Angular dependence measurement revealed Jc peaks for both H(parallel)c and H(parallel)a-b. The peak for H(parallel)c implies additional pinning due to defects such as small angle grain boundaries or twin boundaries. Bending tests at 75 K showed that the YBCO thick films on the metallic substrates could sustain a strain of 0.4% and over 1% for tension and compression, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114559
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