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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    As-deposited high Tc and Jc superconducting thin films made at low temperatures (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 908-910 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 2000 A(ring) as-deposited high Tc superconducting Y1Ba2Cu3O7−x films with zero-resistance temperatures of ∼89 K and critical current densities about 0.7×106 A/cm2 at 77 K have been reproducibly fabricated at a substrate holder temperature of 650 °C, using pulsed laser deposition, with no post-annealing. One key to these results is the injection of gaseous oxygen into the laser-produced plume just in front of the target. In this way, the correct amount of oxygen is incorporated into the as-grown film so that post-deposition treatment becomes unnecessary. The in situ growth of such high Tc and Jc films is an important step in the use of the laser deposition technique to fabricate multilayer structures such as Josephson junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100155
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  • 3
    Electronic Resource
    Electronic Resource
    Low-temperature preparation of high Tc superconducting thin films (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 754-756 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin superconducting films of Y-Ba-Cu-O were prepared at 650 °C using the pulsed laser deposition technique. The as-deposited films were fully superconducting at low temperature (30 K). After annealing in oxygen at 450 °C for 3 h, the films exhibited superconductivity with zero resistance at temperatures as high as 83 K. Film-substrate interface reaction was minimal as revealed by Rutherford backscattering and Auger electron spectrometry. These films processed at such low temperatures are also found to have excellent planar surface morphology and high critical current density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99337
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  • 4
    Electronic Resource
    Electronic Resource
    Optical spectroscopy: An in situ diagnostic for pulsed laser deposition of high Tc superconducting thin films (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 179-181 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High oxygen partial pressure has been found to be an important parameter for the pulsed laser deposition of as-deposited superconducting thin films with high Tc and Jc. The optical emissions from both elemental and oxide species ejected from the target of YBa2Cu3O7−x during the pulsed laser deposition process increase with the oxygen pressure, with the oxide emission showing a stronger pressure dependence than the elemental emission. The dynamics of the interaction between the oxygen atoms and the species in the laser-produced plume were studied by a wavelength and time-resolved measurement. The results are qualitatively explained using a simple model based on optical emission arising from inelastic and recombination collision between the elemental species and electronically excited oxygen atoms. The formation of oxides in the plume is shown to be essential for the production of higher quality superconducting films, indicating the value of optical spectroscopy as a diagnostic tool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101441
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  • 5
    Electronic Resource
    Electronic Resource
    Nature of the pulsed laser process for the deposition of high Tc superconducting thin films (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1431-1433 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pulsed laser thin-film deposition process can enable preparation of thin films of complex composition with good control over the film stoichiometry. The film compositions are similar to that of the target pellet and as a consequence this technique appears to be an ideal method for preparing high Tc thin films on a variety of substrates.The factors which contribute to this beneficial phenomenon have been explored by a laser ionization mass spectrometry (LIMS) and a post ablation ionization (PAI) neutral velocity analysis technique in order to determine the mass and velocities of the laser ejected material. In addition, x-ray absorption measurements on films deposited onto substrates at room temperature were performed in order to identify the presence of short-range crystalline order in the films. Both of these studies rule out the ejection of stoichiometric clusters of material from the pellet during the laser ablation/deposition process. Instead, binary and ternary suboxides are emitted from the target pellet. These suboxides most likely have unit sticking coefficient to the substrate which could contribute to the preservation of the film stoichiometry. The velocity distribution of several neutral species (e.g., BaO) indicates that particles have energies of several eV. Thus the effective temperatures of the emitted species are ∼15×103 K, and these energetic particles may facilitate growth of the crystalline films at low substrate temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100458
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  • 6
    Electronic Resource
    Electronic Resource
    NiAl/n-GaAs Schottky diodes: Barrier height enhancement by high-temperature annealing (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1338-1340 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A metallurgically stable and laterally uniform contact to n-GaAs with an enhanced barrier height (0.99 V) and an ideality factor of 1.10 has been achieved with a NiAl bimetallic metallization. This barrier height, as measured by the forward current-voltage technique after annealing for 20 s at 650 °C, is higher than the reported barrier heights of refractory metallizations to n-GaAs. Auger electron spectroscopy (AES) sputter profiles reveal an Al-Ga exchange reaction after high-temperature (500–950 °C) rapid thermal annealing. From these results, the barrier height enhancement is attributed to the formation of an Al1−xGaxAs layer at the NiAl/n-GaAs interface. The thermal stability and low electrical resistivity of the NiAl phase, the enhanced barrier height on n-GaAs, and the ease of patterning the as-deposited Ni/Al/Ni layered structure by lift-off techniques make NiAl a very promising gate contact material for GaAs metal-semiconductor field-effect transistors and related devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99152
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  • 7
    Electronic Resource
    Electronic Resource
    Superconducting YBa2Cu3O7−x thin films on alkaline earth fluorides (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2032-2034 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alkaline earth fluorides have low dielectric constants and large band gaps. In addition, they are chemically compatible with and several can be grown epitaxially on silicon and compound semiconductors. We have deposited YBa2Cu3O7−x thin films (200–500 nm thick) directly on (001) SrF2, (001) BaF2, (001) MgF2, and unoriented CaF2 single crystals by laser deposition. The substrate temperature was about 720 °C and the vacuum chamber was at 350 mTorr of oxygen. For this work, no additional annealing outside the deposition chamber was done after deposition. The deposited YBa2Cu3O7−x films were superconducting and exhibited transition temperatures Tc (R=0) of 83, 73, and 74 K on MgF2, SrF2, and BaF2, respectively. Structural studies by x-ray diffraction showed that YBa2Cu3O7−x films on MgF2, SrF2, and BaF2 were polycrystalline and exhibited some (00L) textures. Deposition on CaF2 substrates resulted in yellowish, insulating films with Ca- and Ba-rich interfacial reaction products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101507
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  • 8
    Electronic Resource
    Electronic Resource
    Superconducting Y1Ba2Cu3O7−x films on Si (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 243-245 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By depositing YBaCuO films at low substrate holder temperatures (600 °C) using a pulsed laser, films with the orthorhombic phase exhibiting superconductivity with high zero resistance temperatures (Tc0) were produced. Tc0 values as high as 50 and 80 K were seen on films deposited directly on Si and on Si with only a 50 nm ZrO2 buffer layer, respectively. The key to the successful film deposition is the low processing temperatures involved, which minimized the interface reactions as observed by Auger electron spectrometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100588
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