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  • 1
    Electronic Resource
    Electronic Resource
    Prediction of phase formation sequence and phase stability in binary metal-aluminum thin-film systems using the effective heat of formation rule (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3636-3646 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effective heat of formation (ΔH') concept allows heats of formation to be calculated as a function of concentration. In this work the effective heat of formation rule is used to predict first phase formation in metal-aluminum thin-film systems and to predict subsequent phase sequence for thin metal films on thick aluminum or thin aluminum on thick metal substrates. The effective concentration at the growth interface is taken to be that of the lowest temperature eutectic (liquidus) for the binary system. Although the effective heat of formation rule may predict that formation of a certain phase would lead to the largest free energy change, this phase does not necessarily form at the moving reaction interface if it has difficulty to nucleate. By excluding phases with a large number of atoms per unit cell and which thus have difficulty to nucleate, the effective heat of formation rule successfully predicts first phase aluminide formation for all 15 metal-aluminum binary systems for which experimental data could be found. It is also shown how the effective heat of formation rule can be used to predict formation and decomposition of aluminide phases in contact with each other or in contact with their component metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349211
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  • 2
    Electronic Resource
    Electronic Resource
    Optical transitions of a GaSb-AlSb superlattice in the 2–5 eV range (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4007-4008 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report reflectance measurements in the range 2–5 eV of a GaSb-AlSb superlattice grown by molecular-beam epitaxy. In the region of the E1 and E1 + Δ1 transitions, the electronic properties can be related to the formation of electronic subbands of a type II superlattice at the L point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349173
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  • 3
    Electronic Resource
    Electronic Resource
    Above-band-gap photoluminescence from Si fine particles with oxide shell (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1869-1870 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strong photoluminescence with sub-band-gap photon energies has been observed in fine Si particles prepared by the gas-evaporation technique. After surface oxidation, the Si particles show above-band-gap photoluminescence, the band tail covering the visible light region. The amount of the increased apparent band gap (0.3 eV) estimated from this blueshift can be explained by a quantum-size effect expected to be observed in Si quantum dots with a diameter of 50 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349510
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of twin boundaries on flux pinning in YBa2Cu3O7−x at low and intermediate magnetic fields : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5739-5741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic measurements on a single crystal of YBa2Cu3O7−x in the twinned and detwinned states have demonstrated that flux pinning by twin boundaries is strongly dependent upon temperature and the magnitude and orientation of the applied field with respect to the crystallographic orientation. For applied magnetic fields perpendicular to the c axis, no effect of twin boundaries on flux pinning was found at any temperature. In contrast, for fields up to 400 Oe aligned parallel to the c axis, the hysteresis loops at 77 K clearly showed increased pinning due to twin boundaries. At 40 K and low fields (H〈500 Oe) the flux pinning was nearly the same for the twinned and detwinned states, whereas at higher fields (up to 40 kOe), pinning was higher in the twinned state. At this temperature, a tendency toward flux depinning occurred in the detwinned state at about 10 kOe, and both the twinned and detwinned states exhibited a more rigid flux structure at 50 kOe than at 10 kOe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350145
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  • 5
    Electronic Resource
    Electronic Resource
    Fracture toughness of YBa2Cu3O6+δ single crystals: Anisotropy and twinning effects (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5254-5257 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Indentation/crack length measurements were used to determine hardness and fracture toughness in twinned and detwinned single crystals of YBa2Cu3O6+δ (YBCO). Hardness was found to be isotropic and unaffected by twin boundaries or moisture; the average hardness value was 9.5 GPa. Fracture toughness (Kc) was determined to be anisotropic with the average value for cracks running perpendicular to the basal plane being approximately twice that of cracks parallel to the basal plane; thus, cleavage is easier along basal planes. In addition, the results suggest a small but measurable anisotropy in Kc between the a and b directions. Twin boundaries were found to toughen YBCO, enhancing Kc by about 25%. Moisture promoted crack growth, degrading Kc by about 35%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350234
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  • 6
    Electronic Resource
    Electronic Resource
    Mössbauer and magnetic studies of Eu porphyrins (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6022-6022 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first measurements on porphyrin compounds using Eu as the Mössbauer nuclide. There have been many Mössbauer studies on iron porphyrins1,2 and a few on tin.3 We have successfully prepared and made Mössbauer and magnetic susceptibility measurements on four Eu based porphyrin compounds to elucidate the relationship between magnetic properties and structure. Absorption spectra using the 21.6 keV gamma ray of 151Eu were obtained at room temperature and 80 K and yielded very broad singlets with room temperature isomer shift values between 0.20±0.02 mm/s and 0.90±0.02 mm/s with respect to EuF3. Experimental results show the Eu ion to be in the trivalent oxidation state. A discussion of the electronic properties and structure will be reported and compared with previous results found on iron and tin based porphyrins.〈ks〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347799
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  • 7
    Electronic Resource
    Electronic Resource
    Reduction of boron diffusion in silicon by 1 MeV 29Si+ irradiation (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 922-924 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reduction of the transient diffusion of B, implanted in Si along [100] at 10 keV to a dose of 1×1013/cm2, after annealing at 900 °C for 10 s has been observed in samples irradiated with 1.0 MeV 29Si ions to a dose of 5×1013/cm2 or higher. A lower Si dose did not influence the transient B tail diffusion. Secondary defects formed near the peak of the 1 MeV Si damage distribution, for doses of 5×1013/cm2 and higher, act as efficient sinks for interstitials from shallower depths and thereby reduce the transient tail diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104478
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  • 8
    Electronic Resource
    Electronic Resource
    Avoiding preamorphization damage in MeV heavy ion-implanted silicon (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2827-2829 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Implantation of 1.0 MeV 115In in Si results in secondary-defect formation during subsequent 900 °C annealing if the total number of displaced Si atoms is greater than 1.6×1017/cm2, achieved with a dose near 1.5×1013/cm2. We demonstrate, though, that higher total In doses can be introduced without forming secondary defects by repetitive subthreshold implants each followed by an anneal to remove the implant damage. While a single 6×1013 In/cm2 implant results in a high density of dislocation loops after annealing, instead using four separate 1.5×1013 In/cm2 implants each followed by an anneal leads to the formation of only a few partial dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105228
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  • 9
    Electronic Resource
    Electronic Resource
    Breakdown of crystallinity in low-temperature-grown GaAs layers (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2153-2155 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study of the change in structural quality of as-grown GaAs layers deposited at temperatures between 180 and 210 °C by molecular beam epitaxy was performed using transmission electron microscopy, double-crystal x-ray rocking curves, and particle-induced x-ray emission. We found that the crystal quality was correlated strongly with growth temperature near 200 °C. The lattice parameter and the amount of As incorporated in the layer were observed to increase at lower growth temperatures. After exceeding a certain growth-temperature-dependent layer thickness, large densities of pyramidal-type defects are formed, which at lowest growth temperature result in the breakdown of crystallinity and in columnar polycrystalline growth. The lattice expansion is ascribed to the excess As in the layers. The mechanisms of breakdown of crystallinity are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104990
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  • 10
    Electronic Resource
    Electronic Resource
    Low-field flux pinning in twinned and detwinned single crystals of YBa2Cu3O7−x (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1566-1568 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Flux trapping in single crystals of YBa2Cu3O7−x before and after twin removal has been measured for vortices parallel and perpendicular to the c axis. The results show clearly that, for low applied magnetic fields, twins contribute significantly to flux pinning over the temperature range 60 to 85 K when the vortices are parallel to the twin boundaries (i.e., parallel to the c axis).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105180
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