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  • 1
    Electronic Resource
    Electronic Resource
    Optimization of annealing parameters for the growth of epitaxial Ba2YCu3O7−x films on LaAlO3(100) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6353-6360 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The superconducting and structural properties of Ba2YCu3O7−x (BYCO) films on LaAlO3(100) substrates can be improved by carefully optimizing the post-deposition annealing parameters. Films are grown by co-deposition of BaF2, Y, and Cu in the correct stoichiometric ratio to within 1% of 2:1:3. Annealing parameters in an ex situ furnace, including the ambient, annealing temperature, oxidation temperature, and duration of anneals are systematically studied. Films are characterized for epitaxial quality (χmin), morphology, critical temperature (Tc), sharpness of the superconducting transition (ΔT), and critical current density (Jc). For example, beyond simply dissociating BaF2, the use of wet O2 appears to prevent the agglomeration of oxides during the initial heating process, and then act to thermodynamically stabilize the basic BYCO film structure at high temperatures after being formed. Comparisons are made with the best single-crystal BYCO structural and electrical data available. The optimized films have relatively smooth morphology with χmin〈3%, Tc〉90 K, ΔT〈0.5 K, and Jc〉106 A/cm2 in essentially zero magnetic field at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346881
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of growth conditions on the properties and morphology of chemically derived epitaxial thin films of Ba2YCu3O7−x on (001) LaAlO3 (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1868-1877 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of Ba2YCu3O7−x (BYC) were prepared on (001) LaAlO3 single-crystal substrates by metalorganic deposition of metal trifluoroacetate precursors. This is an ex situ process that requires high-temperature annealing in a humid atmosphere to produce stoichiometric BYC thin films. The chemically derived superconducting films were found to have high critical temperatures and high current densities when crystallized under low-oxygen partial pressures. Superconducting films of 70 nm thickness with zero-field critical current densities greater than 5×106 A/cm2 at 77 K and zero resistance at 92 K were prepared by annealing at 780 and 830 °C in 2.5 × 10−4–1 × 10−3 atm oxygen furnace atmospheres. As the film thickness was increased, the superconducting properties and surface smoothness of the films tended to degrade. This behavior was consistent with a microstructural model in which the films are composed of a dense slab of c-axis normal BYC near the film/substrate interface with the overlying material dominated by grains with c-axis in-plane crystallographic orientation. The transport Jc fell to 2–3×106 A/cm2 for films of 200–250-nm thickness annealed at 780 °C in 1 × 10−3 atm oxygen. As the P(O2) was raised to 0.032 atm at 780 °C, for films of the same thickness, the Jc at 77 K decreased to 0.7 × 106–1 × 106 A/cm2 and the Tc(R = 0) dropped to 89 K. Increasing the furnace P(O2) was also found to degrade the crystalline quality of the films, as characterized by ion channeling Rutherford backscattering spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351172
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  • 3
    Electronic Resource
    Electronic Resource
    Growth of pinhole-free epitaxial yttrium silicide on Si(111) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 574-580 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper reports the growth of pinhole-free epitaxial YSi2−x layers on Si(111) as thin as 30 A(ring). This has been accomplished by depositing both Y and Si at room temperature and then annealing to 500–900 °C. Use of the template method allows for the growth of thicker films also free of pinholes. Deposition of yttrium metal only onto Si(111) requires a temperature ∼300 °C for nucleation of the silicide reaction between the Y overlayer and Si substrate. Such a process creates small pinholes ∼500 A(ring) in diameter, randomly distributed throughout the film. These pinholes increase in size with higher annealing temperature, resulting from a raised interface free energy intrinsic to the nucleation controlled growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346809
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  • 4
    Electronic Resource
    Electronic Resource
    Microstructure of epitaxial YBa2Cu3O7−x thin films grown on LaAlO3 (001) (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2268-2270 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a microstructural investigation of the epitaxial growth of YBa2Cu3O7−x (YBCO) thin films on LaAlO3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c axis normal to the surface) and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35–200 nm thick. In 35 nm YBCO films annealed at 850 °C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104165
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of rapid thermal processing on the formation of uniform tetragonal tungsten disilicide films on Si(100) substrates (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 525-529 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of tungsten silicide with resistivities of 30–35 μΩ cm have been formed by sputter depositing 710 A(ring) of W metal onto (100)–oriented, 3–7 Ω cm, p-type silicon wafers. The samples were fast radiatively processed in a rapid thermal processing (RTP) system under high vacuum for time anneals ranging from 15–20 s at two temperatures (∼1100 and ∼1150 °C). The inevitable oxide barrier at the interface is shown to decrease with increasing RTP time and temperature, evidenced by both Auger electron spectroscopy and secondary ion mass spectrometry experiments. The high film stress produced by thermal considerations does not seem to effect the resulting resistivity and, furthermore, appears to relax at higher temperatures when the film surface becomes "buckled.''
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340081
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of dopant and impurity redistributions on WSi2 formation by rapid thermal processing (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 760-766 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin-film samples of WSi2 were formed by sputter depositing tungsten metal directly onto chemically etched, p-type, B-doped, 5 Ω cm Si(100) wafers, followed by rapid thermal processing (RTP) in high vacuum at temperatures over 1100 °C. The resulting dopant and impurity elemental redistributions are studied by secondary ion mass spectroscopy. Boron, initially present both at the W/Si(100) interface as an impurity and in low concentration in the Si substrate, diffuses into the growing WSi2 film, eventually escaping into the vacuum. It is shown that RTP can be used to form high-quality, low-resistivity (∼30 μΩ cm) WSi2 films without total dopant out-diffusion. Oxygen is the major impurity in these samples and is gettered at the metal/Si(100) interface during RTP from the vacuum ambient. Removal of this interfacial oxide is needed for the growth of uniform, low-resistivity silicide films and can be done with RTP. Trace quantities of F, Cl, Na, K, C, and Cr have also been detected. Their origin and movement through the growing silicide films are also monitored as a function of RTP conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343065
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  • 7
    Electronic Resource
    Electronic Resource
    Formation of epitaxial yttrium silicide on (111) silicon (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2999-3006 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of epitaxial yttrium silicide on Si(111) in ultrahigh vacuum is studied. Resistivity, epitaxial quality, and pinhole coverages are studied as a function of annealing temperature for each growth method used. The best films result from the growth of a thin, 30–40-A(ring) template layer which is annealed to 700 °C, followed by a thicker film growth by depositing additional Y onto the substrate heated high enough to induce silicide formation (∼300 °C). Annealing to 900 °C results in a Rutherford backscattering minimum channeling yield χmin ∼3%, which is the same order of epitaxial quality previously achieved by only Ni- and Co-silicide films on silicon. Films grown without templates have larger pinhole sizes with pronounced features indicative of the hexagonal nature of these structures. The deposition of Y metal onto a substrate held at room temperature, followed by annealing to 900 °C results in the lowest resistivities (48 μΩ cm for 425-A(ring) films), but with a highly dislocated film structure featuring 1-μm triangular pits which severely limit epitaxial quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344184
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