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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5635-5641 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the activity and diffusivity of oxygen in liquid Ag-Yb1Ba2Cu3 and Tl1Ba2Ca2Cu3 at 930 and 900 °C, respectively, by a modified coulometric titration method on the galvanic cell: O(underbar) in liquid alloys/yttria stabilized zirconia/air, Pt. The standard Gibbs formation energy and the diffusivity of oxygen in liquid Ag-Yb1Ba2Cu3 alloy for 1/2O2(1 atm)→O(underbar)(1 at. %) are determined to be ΔG=−247.4 kJ/g atom, and D=1.52×10−4 cm2/s. The oxygen solubility Cs in the Ag-Yb1Ba2Cu3 alloy is 0.0913 at. %, a factor of 5.5 higher than that in Yb1Ba2Cu3 alloy. The addition of Ag does not alter the growth mechanism and the oxygen diffusion controls the film growth. The growth speed is enhanced as a result of the enhanced oxygen solubility. ΔG and the diffusion coefficient of oxygen in the Tl1Ba2Ca2Cu3 liquid alloy are −257 kJ/g atom and 1.2×10−4 cm2/s, respectively. The oxygen solubility of the Tl1Ba2Ca2Cu3 alloy at 900 °C is found to be very high at ∼5.74 at. %. All thermodynamic data for oxygen in the precursor alloys are consistent with each other but there is a deviation of activity coefficient with composition for the different alloys from the theoretical model.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 3593-3601 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical deactivation of arsenic in silicon has been studied with regard to its effect on enhanced diffusion. Experimental structures consist of a buried boron layer as an interstitial detector, and a fully activated arsenic doped laser annealed surface layer. As these structures are annealed at temperatures between 500 and 750 °C, arsenic in the surface layer deactivates and we observe enhanced diffusion of the buried boron layer. A study with time reveals that the enhanced diffusion transient and the deactivation transient are similar, indicating a strong correlation between both phenomena. The dependence on concentration shows a maximum enhanced diffusion for concentrations between 3 and 4×1020 cm−3 of initially active arsenic. Above these concentrations, the large supersaturation of interstitials nucleates dislocation loops and lowers the overall enhancement measured in the buried boron layer. Temperature data show that even for temperatures as low as 500 °C, enhanced diffusion is observed. These data are convincing evidence that the enhanced diffusion observed is due to the deactivation of arsenic and provides important insights into the mechanisms of deactivation. We propose that arsenic deactivation forms small clusters of various sizes around a vacancy with the injection of an associated interstitial into the bulk. © 1998 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4737-4740 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Selectively red shifting the photoresponse of intersubband GaAs/Al0.25Ga0.75As multiple-quantum-well (MQW) infrared photodetectors (QWIPs) by furnace and rapid thermal annealing is explored. Selective interdiffusion of the MQW is achieved by dielectric encapsulating (SiO2 or Si3N4) the surface. The high dark current of annealed QWIPs is attributed to dopant out-diffusion from the QWs into the barriers. Declining responsivities result from reduced carrier density in the QW and a red shift of the intersubband transition energy. In this work, the intersubband energy is determined by the Fourier synthesis model and compared with experimental results (further confirming the interdiffusion mechanism). Minimal dark current and responsivity degradation is observed for Si3N4-encapsulated QWIPs red shifted by 1 μm © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co(11¯00)/Cr(211) and Co(112¯0)/Cr(100) multilayers have been simultaneously prepared on MgO(110) and MgO(100) substrates, respectively, by molecular beam epitaxy. They show however distinct magnetic anisotropic behavior which coincides with their magneto–crystalline anisotropy. Magneto–optical Kerr effect shows the existence of a unique easy axis and strong in-plane uniaxial magnetic anisotropy in Co(11¯00)/Cr(211) multilayers, which is induced by the well-defined hexagonal crystalline of the Co(11¯00) layers. For Co(112¯0)/Cr(100) multilayers, on the other hand, an in-plane biaxial magnetic anisotropy is found due to the bicrystalline structure of the Co(112¯0) layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 760-762 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The activity and diffusivity of oxygen in a liquid Yb1Ba2Cu3 high temperature superconducting precursor alloy have been measured by modified coulometric titration method in a temperature range from 913 to 957 °C. The standard Gibbs formation energies and the diffusivity of oxygen in liquid Yb1Ba2Cu3 for 1/2O2 (1 atm)→O (1 at. %) are determined to be ΔG=−655.20+0.335T(K) (±1.5) kJ/mol and D=1.8×10−2 exp(−48 100/RT) (cm2/s) where R=8.314 J/deg×mol. Despite very strong bonding of oxygen to the liquid alloys, the diffusion coefficient of oxygen is relatively high in the order of 10−4 cm2/s. The solubility of oxygen in the liquid alloy is low, of about 0.0145 and 0.017 at. % at 913 and 935 °C, respectively.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 751-753 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a theoretical prediction of the threshold current density and the temperature sensitivity of a GaN laser operating in the intrinsic band-to-band transition. We calculate the material gain and spontaneous emission spectrum for unintentionally doped bulk GaN under carrier injection. All stimulated and spontaneous emission calculations are compared to those of bulk GaAs. The transparency carrier density of GaN is found to be more than four times that of GaAs, and the momentum matrix element for optical transitions in bulk GaN is estimated to be about one-third the value in GaAs. In addition, the differential gain is approximately four times smaller in GaN. These differences are attributed to the larger effective masses of the electrons and holes in GaN. The calculated characteristic temperature T0 of the threshold current density for a GaN laser ranges from 185 to 220 K, which agrees well with the recently observed data from optical pumping experiments. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 796-798 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A consistent method to characterize the temperature dependence of bulk InGaAsP semiconductor laser diodes is presented. Independent measurements of the gain and spontaneous emission spectra are conducted, and the spectra are calibrated using their fundamental relationship. This procedure will provide a unique approach to extract precise values for laser diode parameters such as quasi-Fermi level separation, peak modal gain, and total loss. The radiative and nonradiative current densities can then be calculated as a function of temperature and injection current. By comparing the measured data with a theoretical model, the carrier density is calculated. Important phenomena contributing to the strong temperature dependence of long-wavelength bulk InGaAsP/InP lasers are highlighted. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3573-3575 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of laser annealing on important detector characteristics such as dark current, spectral response, and absolute responsivity is investigated for bound-to-continuum GaAs/AlGaAs quantum-well infrared photodetectors (QWIPs) operating in the 8–12 μm wavelength regime. A set of experiments was conducted on QWIPs fabricated from both as-grown and laser-annealed multiple-quantum-well structures. Compared to the as-grown structure, the peak spectral response of the laser-annealed structure was shifted to longer wavelengths, though absolute responsivity was decreased by about a factor of two. In addition, over a wide range of bias levels, the laser-annealed QWIPs exhibited a slightly lower dark current compared to the as-grown QWIPs. Thus, the postgrowth control of GaAs/AlGaAs quantum-well composition profiles by laser annealing offers unique opportunities to fine tune various aspects of a QWIP's response. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 78-80 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we describe the characteristics of molecular beam epitaxy GaAs/AlGaAs quantum-well infrared photodetectors (QWIP's) grown on a GaAs substrate, and on a GaAs-on-Si substrate produced by metalorganic chemical-vapor deposition. Important issues for QWIP applications such as dark current, spectral response, and absolute responsivity are studied. We find that compared to a similar detector structure grown on a GaAs substrate, the detector grown on a GaAs-on-Si substrate exhibits similar dark current and absolute responsivity while displaying a small blueshift in the spectral response. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 407-409 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnO nanowires were mass produced using a physical vapor deposition approach. The ZnO nanowire monocrystallites have an average diameter around 60 nm and length up to a few micrometers. The unidirectional growth of the ZnO nanowires was controlled by the conventional vapor-liquid-solid mechanism. Intensive UV light emission peaked around 3.27 eV was observed at room temperature, which was assigned to emission from free exciton under low excitation intensity. The observed room temperature UV emission was ascribed to the decrease in structure defects as compared to bulk ZnO materials, and in particularly to the size effect in the ZnO wires. © 2001 American Institute of Physics.
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