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  • 11
    Electronic Resource
    Electronic Resource
    Mechanical and high-temperature (920 °C) magnetic field grain alignment of polycrystalline (Ho,Y)Ba2Cu3O7−δ (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3136-3141 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of uniaxial compression, high-temperature (920 °C) heat treatment, and heat treatment plus magnetic field on grain alignment in bulk ceramic pellets of HoBa2Cu3O7−δ and YBa2Cu3O7−δ were studied and separated. Uniaxially cold pressing prereacted powder into pellets at room temperature is found to yield significant grain alignment on the flat end surfaces of the pellets perpendicular to the pressing axis, where the c axes of the grains are parallel to this axis, in agreement with previous reports. A simple method to quantitatively determine the degree of surface grain alignment from the powder x-ray diffraction data from these surfaces is used. These data were augmented by x-ray rocking curve measurements. The degree of alignment of the cold pressed samples was found to increase with increasing pressure up to our pressure limit of 310 MPa. However, bulk magnetization anisotropy measurements on these pellets indicate that the degree of bulk alignment is only about 1/3 to 1/2 that inferred from the above surface measurements, which in turn suggests that the degree of alignment decreases with distance from the flat end surfaces. We find that a pronounced additional surface grain alignment is produced by heat treating the cold-pressed samples at high temperature (920 °C). We also observed a significant influence during the high-temperature annealing of a small (0.7 T) applied magnetic field on the alignment of the surface grains. A model to explain these observations is presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342710
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  • 12
    Electronic Resource
    Electronic Resource
    Room temperature study of low temperature grown Al0.3Ga0.7As/GaAs multiple quantum wells by modulation reflectance (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8589-8593 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied the subband energy levels in AlGaAs/GaAs multiple quantum wells grown at different temperatures (200–600 °C) by using the piezoreflectance and photoreflectance in room temperature. Under subsequent 30 s rapid-thermal annealing at different temperatures (600–1000 °C), we observed a large energy blueshift in samples with growth temperature below 400 °C. This blueshift energy may be attributed to the modification of quantum wells caused by gallium vacancy enhanced Al–Ga interdiffusion. The energy blueshifts were analyzed by solving Fick's second law for Al diffusion in quantum wells, obtaining an effective activation energy of 0.75 eV. We discuss our results using the nonequilibrium diffusion equation and comparing them with other experiments. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373583
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  • 13
    Electronic Resource
    Electronic Resource
    Memory effects related to deep levels in metal–oxide–semiconductor structure with nanocrystalline Si (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2502-2504 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanocrystalline(nc)-Si was grown on SiO2 by rapid thermal chemical vapor deposition. The tunneling oxide layer of a thickness of 4 nm was formed on p-type Si(100) by rapid thermal oxidation at 1050 °C for 30 s. Metal–oxide–semiconductor (MOS) structures were fabricated and capacitance–voltage characterization was carried out to study the memory effects of the nc-Si embedded in the MOS structure. We found the memory effect to be dominantly related to hydrogen-related traps, in addition to being influenced by the three-dimensional quantum confinement and Coulomb charge effects. Deep level transient spectroscopy reveal that the activation energies of the hydrogen-related traps are Ev+0.29 eV (H1) and Ev+0.42 eV (H2), and the capture cross sections are 4.70×10−16 cm2 and 1.44×10−15 cm2, respectively. The presence of Si(Single Bond)H and Si(Single Bond)H2 bonds was confirmed by Fourier transform infrared spectroscopy. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1467617
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  • 14
    Electronic Resource
    Electronic Resource
    The Fermi level of annealed low-temperature GaAs on Si-δ-doped GaAs grown by molecular beam epitaxy (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 486-490 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance has been used to study the Fermi level of annealed low-temperature GaAs in sample structures composed of low-temperature GaAs on top of Si-δ-doped GaAs. The diffusion of As precipitates across the interface between low-temperature GaAs and normal GaAs is observed by cross-sectional imaging via transmission electron microscopy. We have calculated the Fermi-level pinning in low-temperature GaAs by including the Si-δ-doped carrier concentration correction due to the accumulation of As precipitates. The Fermi level is found to decrease from 0.7 to 0.5 eV below the conduction band when the annealing temperature is increased from 600 °C to 900 °C. This may be explained with the buried Schottky barrier model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366719
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  • 15
    Electronic Resource
    Electronic Resource
    A study of the Franz–Keldysh oscillations in electromodulation reflectance of Si-delta-doped GaAs by a fast Fourier transformation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7873-7878 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The line shapes of electromodulation spectra exhibit extended Franz–Keldysh oscillations and interference beats in the presence of a uniform built-in electric field. For this work, we used photoreflectance and contactless electroreflectance to study the Franz–Keldysh oscillations in Si-delta-doped GaAs. The fast Fourier transformation taken to the photoreflectance and contactless electroreflectance spectra, produced more complicated results than were observed in previous studies, when the effect of the modulation field is nonnegligible. This indicates that the interference beats are not only due to different effective heavy-hole and light-hole mass but also to the modulation field. We propose that the Franz–Keldysh oscillations generally contain four frequencies, which correspond to the heavy-hole and light-hole splitting. A comparison between the experiments and some numerical simulations attest to the validity of our proposal. This line shape analysis could then be applied to estimate the strength of a modulation field in contactless electroreflectance and photoreflectance. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367964
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  • 16
    Electronic Resource
    Electronic Resource
    Pumping-beam-induced photovoltaic effect on the photoreflectance of a δ-doped GaAs film (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6980-6983 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoreflectance (PR) spectroscopy of a δ-doped GaAs film has been measured at 300 K. Results reveal many Franz–Keldysh oscillations (FKOs) above the band-gap energy, which will enable the electric-field strength to be determined from the periods of FKOs. Since the photovoltaic effect cannot be neglected in PR measurements when using light as both the pumping and probing beams, it is generally assumed that the modulation field δF is much smaller than the built-in field F so that the periods of the FKOs will not be affected by the pumping beam. However, the induced photovoltage can be over 2/3 of Fermi level at low temperatures and cannot be neglected even at room temperature. Hence, the finite value of δF needs to be taken into consideration. The effect of δF on the shapes of PR is discussed, and it is shown that the FKOs of PR oscillate at a frequency corresponding to F−δF/2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363771
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  • 17
    Electronic Resource
    Electronic Resource
    Fast Fourier transformation of piezoreflectance in δ-doped GaAs (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1074-1080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Franz–Keldysh oscillations in Si-δ-doped GaAs have been studied by the application of fast Fourier transformations to the piezoreflectance spectra. In such studies, we find that the Franz–Keldysh oscillations of the piezoreflectance and its associated Fourier transformation can be described by a model calculation which considers the energy gap modulation in a uniform electric field. Owing to the character of nonelectromodulation, the Franz–Keldysh oscillation lineshape in the piezoreflectance has no modulation electric field distortion such as that which occurs in the photoreflectance and electroreflectance experiments. We demonstrate that the piezoreflectance accuracy is better than the photoreflectance or electroreflectance for the measurement of a uniform built-in electric field. The fast Fourier transformation of piezoreflectance spectra exhibits two separate heavy- and light-hole frequencies at temperatures from 20 to 425 K. Using these separated peaks, the ratio between the heavy- and light-hole effective reduced mass, the surface Fermi level, and the broadening parameters of the Franz–Keldysh oscillations are measured and discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368106
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  • 18
    Electronic Resource
    Electronic Resource
    Electromodulation reflectance of low temperature grown GaAs (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2603-2606 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied low temperature grown GaAs by electromodulation reflectance spectroscopy for growth temperatures between 200 and 320 °C. The reflectance spectra can be observed only when the concentration of the arsenic antisite defect is lower than 3.4×1019 cm−3. The absence of the signal for a rich defect sample is related to the short carrier lifetime and surface depletion width. The transition energies of E0 and E1 are found to increase with the decrease of the growth temperatures. The increase of the transition energies is attributed to lattice mismatch and deviation of the stoichiometry. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366073
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  • 19
    Electronic Resource
    Electronic Resource
    Plate-height equation for non-linear chromatography
    Amsterdam : Elsevier
    Journal of Chromatography A 606 (1992), S. 153-163 
    Details
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0021-9673(92)87020-9
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  • 20
    Electronic Resource
    Electronic Resource
    Effect of metal counterions on the stereoselectivity of aldol reactions used to assemble the seco acid backbone of erythromycin b
    Amsterdam : Elsevier
    Tetrahedron Letters 34 (1993), S. 2711-2714 
    Details
    ISSN: 0040-4039
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4039(00)73542-8
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