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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3195-3202 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The diffusion and release of H and its uptake from the gas phase are modeled for Mg-doped, wurtzite GaN using formation energies and vibration frequencies from the density-function theory. Comparison is made with rates of deuterium release and uptake measured by nuclear-reaction analysis of deuterium concentration. Good agreement is found when account is taken of a surface permeation barrier. © 2001 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3758-3762 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photostimulated luminescence (PSL) phosphors, such as BaFBr:Eu, are currently used in x-ray screens for digital medical imaging. There is, however, little known about the mechanistic details responsible for the luminescence process in these materials. This paper describes a study of the emission mechanism in the host lattice BaFX(X=Cl, Br). Electron-hole recombination luminescence produced by x-ray irradiation has been observed. The recombination luminescence intensity is temperature dependent and yields information concerning the ionization process in these crystal lattices. This information is fundamental to the PSL process.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4676-4687 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation energies and vibration frequencies for H in wurtzite GaN were calculated from density-functional theory and used to predict equilibrium state occupancies and solid solubilities at elevated temperatures for p-type, intrinsic, and n-type material. The solubility of deuterium (D) was measured in p-type, Mg-doped GaN at 600, 700, and 800 °C as a function of D2 pressure and compared with theory. Agreement was obtained by reducing the H formation energies 0.22 eV from ab initio theoretical values. The predicted stretch-mode frequency for H bound to the Mg acceptor lies 5% above an observed infrared absorption attributed to this complex. More limited solubility measurements were carried out for nominally undoped material rendered n-type by donors provisionally identified as O impurities, and results agree well with theory after the aforementioned adjustment of formation energies. It is concluded that currently recognized H states and physical processes can account for the equilibrium, elevated-temperature behavior of H examined in this work. © 2000 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 805-807 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We conducted a series of numerical experiments to study the propagation of laser-supported detonation waves (LSDWs) in the case that a CO2 laser beam strikes an aluminum surface obliquely in air. A reflected shock formed at the aluminum surface was more prominent at higher angles of incidence θ of the beam, but otherwise the hydrodynamics of the plasma and the LSDW were insensitive to θ. Furthermore, the total impulse delivered to the aluminum varied approximately as 1/cos θ, a result that can be modeled with elementary blast-wave theory.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5371-5380 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Variations in the concentrations and distributions of the OH− defects present in flux and hydrothermal KTiOPO4 (KTP) crystals, measured by infrared spectroscopy of single crystals, are attributed to differences in the growth environments and other nonhydrogenic defects present in the crystals. The concentrations of OH− have been estimated from the infrared data to be approximately 400 ppma (parts per million atomic) (3.0×1019 cm−3) in the flux crystals, 1100–1500 ppma (0.74–1.1×1020 cm−3) in the high-temperature hydrothermal and 600 ppma (4.3×1019 cm−3) in the low-temperature hydrothermal crystals. A 3566 cm−1 peak and a 3575 cm−1 band are observed in all crystals. The integrated intensity of the OH− absorption band at 3566 cm−1 increases at the expense of the 3575 cm−1 band at higher temperatures in the high-temperature hydrothermal crystals. Several OH− peaks (3490, 3455, 3428, 3420, and 3333 cm−1), which have strongly temperature-dependent linewidths, are present in the hydrothermally grown KTP crystals. The temperature dependencies of their peak frequencies and widths are consistent with the presence of mobile protons in the lattice. The protons located in the 3490 and 3428 cm−1 sites are believed to contribute to the ionic conductivity of the high-conductivity high-temperature hydrothermal crystals.
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 102 (1980), S. 3728-3732 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1688-1690 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the growth and characterization of ultraviolet GaN quantum well light emitting diodes. The room-temperature electroluminescence emission was peaked at 353.6 nm with a narrow linewidth of 5.8 nm. In the simple planar devices, without any efforts to improve light extraction efficiency, an output power of 13 μW at 20 mA was measured, limited in the present design by absorption in the GaN cap layer and buffer layer. Pulsed electroluminescence data demonstrate that the output power does not saturate up to current densities approaching 9 kA/cm2. © 1998 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 966-968 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Picosecond photoinduced absorption measurements have been performed on four different (AlxGa1−x)0.5In0.5P fractal quantum well heterostructures. The results of these measurements reveal that, at early times following pulsed excitation, the carriers remain near the surface layer in which they were photogenerated, and populate the higher lying branches of the V-shaped fractal structure. With increasing time, the carrier population relaxes toward the lowest energy, central wall. The rate at which the relaxation occurs is governed by the characteristic layer of widths of the fractal structure.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3689-3691 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an experimental and theoretical analysis of the threshold properties of infrared oxide-confined vertical-cavity surface emitting lasers. We find good agreement between experiment and theory on the wavelength dependencies of the threshold current density and intrinsic voltage. The threshold voltage is shown to equal the sum of the calculated quasi-Fermi energy separation and the ohmic drop arising from a record low 17 to 30 Ω series resistance in these vertical-cavity lasers. Our analysis provides two independent means for determining the material threshold gain. A threshold gain of 500 cm−1 is found for these oxide-confined lasers, which is half that estimated for ion-implanted lasers with inferior electrical and optical confinement. © 1996 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 200-202 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rapid thermal annealing of GaN in an Ar or N2 ambient up to 1100 °C is shown to improve surface morphology and photoluminescence intensity. For both ambients the average rms surface roughness as determined by atomic force microscopy decreases from ∼4 nm on the as-grown material to ∼1 nm after a 1100 °C anneal. The band-edge luminescence intensity was increased by a factor of 4 after a 1100 °C anneal in a N2 ambient and a factor of 2 for annealing at 1100 °C in an Ar ambient as compared to as-grown material. The 1100 °C anneal improves the ratio of band edge to deep-level luminescence and also reduces the electron concentration and mobility. The reduction in mobility can be explained in terms of a two-band conduction mechanism where defect band conduction dominates at the lower carrier densities or an increase in the free-carrier compensation ratio. © 1996 American Institute of Physics.
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