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  • 1
    Electronic Resource
    Electronic Resource
    Transport properties of silver-doped Y-Ba-Cu-O thin films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1538-1542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transport properties of dilute silver-doped Y-Ba-Cu-O thin films prepared by a laser ablation technique have been investigated. The Hall coefficient and critical current density were measured as a function of temperature and in magnetic field up to 1.0 T. Silver doping is shown to result in significant changes in the temperature- and magnetic-field dependence of the transport properties of these films. The Hall coefficient in silver-doped films shows a clear decrease from that in silver-free films, consistent with an increase in the hole concentration caused by the silver impurities. This result lends a direct support to the observation that dilute silver dopants behave as acceptors but without appreciable influence on the transition temperature. The magnetic-field dependence of the normalized critical current density Jc(H)/Jc(0) is enhanced by silver doping, mainly due to a decrease in the effective weak-link area at the grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347245
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of interfacial roughness of InxGa1−xAs epitaxial layers on GaAs and InP substrates by soft x-ray reflectivity (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 949-953 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The grazing incidence x-ray reflectivity is a nondestructive and sensitive technique for probing the depth profile of electron density in layered structures. This method has been utilized in the soft x-ray regime to determine the roughness of interfaces, and the epilayer thickness in InxGa1−xAs/InP and InxGa1−xAs/GaAs heterostructures, for x=0.57 and x=0.60, grown by molecular beam epitaxy. By fitting the experimental results to our model, assuming uncorrelated interfacial roughness, we conclude that the top surface roughness does not depend on the type of the substrate or presence of stress in the epilayer, and is always smaller than interfacial roughness. The main factors which control the interfacial roughness are the quality of substrate and/or growth conditions rather than strain or lattice mismatch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347338
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  • 3
    Electronic Resource
    Electronic Resource
    Instability in surface emitting lasers due to external optical feedback (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 16-20 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Instability in the output of dc-biased surface emitting lasers due to an external cavity effect was observed. The output power spectrum exhibited multiple peaks with spacing corresponding to exactly the round-trip delay in silica fibers with length ranging from 2 m to 2 km. The magnitude of the peaks was enhanced in the spectral region centered at the laser relaxation frequency. With increased feedback, the background of the output spectrum was found to increase, indicating the presence of optical chaos. Numerical simulation based on the rate equation analysis was found to agree with the experiment, indicating the surface emitting lasers are well described by the rate equation and are susceptible to feedback as the edge emitting lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353880
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of SiO2/Si heterostructures by soft x-ray reflection (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1631-1642 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grazing incidence x-ray reflectivity has been used to characterize four as-grown SiO2/Si(100) heterostructures with SiO2 overlayer thicknesses ranging from about 126 to 1100 A(ring). Root-mean-square roughness at both the top surface and buried interface is determined, as is the (complex-valued) x-ray refractive index of the SiO2 heterostructure material for photons in the energy range 400–800 eV. Knowledge of the SiO2 and Si refractive indices allows the oxygen atomic scattering factor to be deduced at these energies. Evidence that one of the four thermally grown structures may consist of more than just a single homogeneous overlayer is also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347260
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  • 5
    Electronic Resource
    Electronic Resource
    Migration of constituent atoms and interface morphology in a heterojunction between CdS and CuInSe2 single crystals (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6052-6058 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Angular dependence of x-ray fluorescence (ADXRF), x-ray absorption fine structure (XAFS), and grazing incidence x-ray scattering measurements were carried out using synchrotron radiation for a study of the interface morphology and migration of constituent atoms in a heterojunction formed between CdS and CuInSe2 single crystals. The advantage of using a single crystal for this study is to avoid the usually complicated problems arising from multiple phases of the Cu–In–Se compounds. By a comparison of the results obtained with a bare CuInSe2 single crystal, the changes of interface microstructures in the CdS/CuInSe2 heterojunction system with well-defined stoichiometry can therefore be investigated. Prominent features in the ADXRF data clearly demonstrate that both Cu and Se atoms have migrated into the CdS layer in the heterojunction while In atoms remain intact in the CuInSe2 single crystal. The local structures around Cu in the system also show a significant change after the deposition of CdS, as manifested by the appearance of new Cd near neighbors in the XAFS spectra. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371653
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  • 6
    Electronic Resource
    Electronic Resource
    Raman effect in AlGaAs waveguides for subpicosecond pulses (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2198-2203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Raman effect in semiconductor waveguides below half-gap is studied both experimentally and numerically. We report the depolarized Raman gain spectra up to 300 cm−1 in Al0.24Ga0.76As at pump wavelengths of 0.515 and 1.55 μm from the measurement of the absolute Raman scattering cross sections using GaAs as a reference scatterer. In addition, the coupled propagation equations for the AlGaAs waveguides are modified to include the Raman effect. By solving the coupled propagation equations numerically, we verify that the energy transfer between two orthogonally polarized pulses demonstrated in previous pump-probe experiments [M. N. Islam et al., J. Appl. Phys. 71, 1927 (1992)] is caused by Raman effect. We also show numerically that the Raman effect induces spectral distortions on the pulses, and the energy transfer is inversely proportional to the pulse widths. The energy transfer results in a severe cross-talk problem for sub-picosecond pulses in AlGaAs waveguides. For example, the energy exchange is about 30% for 300 fs pulses under π phase shift conditions. Therefore, the Raman effect limits the performance of semiconductor waveguides in optical switching applications for sub-picosecond pulses. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360135
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  • 7
    Electronic Resource
    Electronic Resource
    Structural ordering in InGaAs/GaAs superlattices (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4372-4376 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Various x-ray techniques have been applied to a study of semiconductor superlattices consisting of 100-period of InxGa1−xAs (15 A(ring))/GaAs (100 A(ring)) grown on GaAs(100) substrates by molecular beam epitaxy. Structural parameters pertaining to the morphology of interfaces and thickness variations were obtained. The interfaces in these superlattices are found to be highly correlated, and the layers all show a high degree of crystallinity. Splittings in the x-ray reflectivity and diffraction patterns in one of the samples provide clear evidence for pronounced thickness modulation, and direct comparison of the diffraction satellite peaks with results of high resolution transmission electron microscopy indicates that there exists a lateral structural ordering in the [110] direction during epitaxial growth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363421
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray scattering and absorption studies of MnAs/GaAs heterostructures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1435-1440 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic MnAs thin films grown on GaAs (001) substrates by molecular-beam epitaxy have been studied by the methods of grazing incidence x-ray scattering, x-ray diffraction, and extended x-ray-absorption fine structure. Microstructures in two films prepared with different first-layer growth conditions (template effects) are compared in terms of the interfacial roughness in the layer structure, lattice constants, epilayer thickness, local environment surrounding the Mn atoms, coordination number, and local disorder. Our results indicate that the template effects can cause significant differences in the local structures and crystallinity of the MnAs epitaxial layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360981
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  • 9
    Electronic Resource
    Electronic Resource
    Critical current density enhancement in YBa2Cu3O6.8 films on buffered metallic substrates (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1202-1204 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A transition buffer, consisting of subbuffers grown at different temperatures, was used to enhance the crystallinity and the transport properties of YBa2Cu3O6.8 (YBCO) films on metallic substrates. Films were fabricated using in situ laser deposition and were strongly c-axis oriented. Critical temperature of 87 K and critical current density of 3×104 A/cm2 at 77 K were obtained for a 0.5-μm-thick YBCO film with a 0.2 μm transition yttrium- stabilized ZrO2 buffer layer. Also, the magnetic field dependence of Jc could be enhanced by using Pt-coated metallic substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104364
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  • 10
    Electronic Resource
    Electronic Resource
    Annealing effects and Te mixing in CdTe/CdS heterojunctions (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 218-220 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Angular dependence of x-ray fluorescence techniques have been employed to investigate the effects of thermal annealing at various temperatures ranging from 340 to 387 °C on a series of CdTe/CdS heterojunctions. Changes in depth profiles of Te and Cd atoms in the CdS layer as a result of heat treatment has been observed. A simple model is proposed for comparison of the ratio of Te Kα to Cd Kα fluorescence yield at different annealing temperatures. Our results suggest that the concentration of migrated Te atoms in the CdS layer increases with the annealing temperature, and the Te/Cd ratio in the CdS layer could even become greater than that in CdTe with annealing temperatures higher than 370 °C. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123298
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