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  • 1
    Electronic Resource
    Electronic Resource
    Optical absorption spectrum of hydrogenated amorphous silicon using photo-pyroelectric spectroscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1799-1804 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical absorption coefficient α of doped and undoped hydrogenated amorphous silicon (a-Si:H) has been measured for photon energies from 2.2 to 1.0 eV using photo-pyroelectric spectroscopy (PPES). A simplified experimental setup and analysis for extracting α from the PPES data are described. In PPES the temperature rise induced in the a-Si:H thin film due to weakly absorbed light is detected via a pyroelectric polymer in thermal contact with the sample. This technique presently has a sensitivity of αd(approximately-greater-than)10−3, where d is the sample thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354784
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of thin protective InAs layers on the optical quality of AlGaAs and quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2449-2452 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Influence of a thin protective but subsequently evaporated InAs layer on the regrowth of AlGaAs has been studied. It was found that although most of the InAs could be evaporated by thermal desorption, some would react with Al0.36Ga0.64As to form InAlGaAs. These InAlGaAs islands act as potential wells for carrier recombination and dominate the photoluminescence spectrum. Transmission electron microscopy photographs show that dislocations are formed near the islands. These defects are caused by lattice mismatch between AlGaAs and InAlGaAs. These islands and defects strongly affect the optical quality of surrounding Al0.36Ga0.64As and quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351590
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  • 3
    Electronic Resource
    Electronic Resource
    Transmission electron microscopy study of heavily delta-doped GaAs grown by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 608-614 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: N-type and p-type delta-doped GaAs grown by molecular beam epitaxy with rather significantly high doses of Si and Be have been investigated by transmission electron microscopy (TEM). The amount of doses ranged from half a monolayer to two monolayers. The microscopic structures of the delta-doped regions and the adjacent epilayers were directly observed by TEM. The effect of impurity spreading on the heterointerfaces and superlattices was also studied. Si atoms present in Si delta-doped samples were confined to within a few atomic layers. The Be atoms present in Be delta-doped samples, however, spread over a quite wide region and caused rough heterointerfaces and wavy superlattices to form. Spreading of Be was attributed to segregation and diffusion which occurred during growth. Stacking faults were found in the delta-doped samples when they were grown at low temperatures. They could be attributed to local strain caused by heavy doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353370
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  • 4
    Electronic Resource
    Electronic Resource
    Two-laser resonance-enhanced photoionization spectrum of benzene (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3490-3497 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper reports results of an experiment involving two-laser resonance-enhanced photoionization of benzene. The excitation sources were two frequency-doubled dye lasers. The first laser pumped the molecule to a selected vibronic level of its first excited singlet state (1B2u), from where it was ionized by a time-delayed pulse of the second laser. The ion yield depends on the intermediate vibronic state as well as on the wavelength of the ionizing laser. From the structures and intensities of the measured ion spectra we derived vibrational frequencies and molecular parameters of the ground electronic state of the ion to a remarkable accuracy. The contributions of autoionizing Rydberg levels to the ionization cross section can clearly be distinguished from direct ionization. Several resonance peaks were assigned to transitions to vibrational modes within these Rydberg states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455859
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  • 5
    Electronic Resource
    Electronic Resource
    Above-barrier states in GaAs–AlGaAs superlattices studied by photoconductivity and photoreflectance (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1460-1462 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report that the quasibound states at the above-barrier region in AlGaAs–GaAs superlattices can be clearly observed at room temperature by photoconductivity as well as photoreflectance measurements. We provide concrete evidence to confirm that free-carrier confinement at barrier layer does exist. It is also found that the barrier-width dependence of the above-barrier transition energies can be described quite well by the modified Messiah's calculation. However, the simple calculation using the constructive interference condition can only explain the transitions at lower energies, and fails with increasing transition energy. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370965
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  • 6
    Electronic Resource
    Electronic Resource
    An efficient gene transduction system for studying gene function in primary human dermal fibroblasts and epidermal keratinocytes (2003)
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 28 (2003), S. 0 
    Details
    ISSN: 1365-2230
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary One of the critical challenges for cellular genetic studies in primary human skin cells is lack of a gene delivery system that provides efficient transduction and sustained expression of the transgenes. Due to the limited time of survival in culture, the processes of drug selection and clonal expansion for establishing gene stably expressing cell lines are not a realistic option for primary skin cells. We have examined various gene transduction techniques in primary dermal fibroblasts and epidermal keratinocytes of human skin. We report here that vectors based on the human immunodeficiency virus (HIV, lentivirus) offer more than 90% gene transduction efficiency and sustained expression of transgenes in both human skin cell types. In contrast, most of the commonly used techniques have at best 30% transduction efficiency in these cells. Using two previously reported migration control genes, protein kinase Cδ and p38α-MAPK, as examples, we provide evidence that the unprecedented efficiency of the lentiviral system enables a clear detection of the genes' dominant negative effects, which are otherwise greatly compromised by ordinary transfection techniques. We believe that a wide application of this gene transduction system will greatly benefit studies of gene function in human skin cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2230.2003.01191.x
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  • 7
    Electronic Resource
    Electronic Resource
    The Behavior of γ-Keto- and Aldehydo-Acid Derivatives at the Dropping Mercury Electrode. III. 3-(p-Bromobenzoyl)-3-methylacrylic Acid Derivatives1 (1945)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 67 (1945), S. 1300-1302 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01224a027
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  • 8
    Electronic Resource
    Electronic Resource
    Compositional disordering of InGaAs/GaAs heterostructures by low-temperature-grown GaAs layers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 664-670 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Compositional disordering of InGaAs/GaAs superlattices using a low-temperature-grown GaAs cap layer (LT-GaAs) by molecular beam epitaxy has been studied. The disordering of the superlattice was verified by photoluminescence and double-crystal x-ray rocking curve measurements. The Ga-vacancy-enhanced interdiffusion due to the presence of LT-GaAs was found to be the disordering mechanism. Diffusion equations and the Schrödinger's equation were solved numerically to obtain the composition profile and the transition energies in the disordered quantum well, respectively. The simulated energy shifts for samples under different annealing conditions agreed very well with the experimental results. The calculated effective diffusivity for the In–Ga interdiffusion has an activation energy of 1.63 eV, which is smaller than the activation energy 1.93 eV, for intrinsic interdiffusion. The diffusivity for the enhanced In–Ga interdiffusion due to the presence of LT-GaAs is about two orders of magnitude larger than the intrinsic In–Ga diffusivity. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360810
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal reactions of Pd/AlxGa1−xAs contacts (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2891-2895 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pd/AlxGa1−xAs Schottky contacts and their thermal reactions are studied by capacitance–voltage measurements, current–voltage measurements, and x-ray diffraction. The thickness of AlxGa1−xAs consumed by the Pd/AlxGa1−xAs reaction during annealing was calculated. For annealing temperatures below 300 °C the Schottky characteristics of the diodes were good but the electrical junction moves into AlxGa1−xAs after annealing. The amount of junction movement was calculated directly from our measurements. The diffusion coefficients of Pd in AlxGa1−xAs and the activation energy were estimated. The activation energy was found to be larger for higher Al concentration. PdAl, PdAs2, PdGa5, and Pd5Ga2 were detected in the compounds formed by the Pd/AlxGa1−xAs reaction after annealing. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363141
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  • 10
    Electronic Resource
    Electronic Resource
    Enhancement of conduction-band effective mass in III–V semiconductor alloys induced by chemical disorder (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6761-6765 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conduction-band effective masses in InxGa1−xAs with a complete range of composition, and InAlGaAs and InGaAsP alloys covering the complete range of lattice matched to InP have been determined by far-infrared optically detected cyclotron resonance and magnetophotoconductivity measurements. It is found that the measured effective masses as a function of alloy composition are heavier than the values predicted from the five-band k⋅p theory. We show that this discrepancy can be resolved by including the effect of disorder-induced potential fluctuations that causes the wave function mixing between conduction and valence bands. We find that the strength of the potential fluctuations can be well described in terms of the Phillips electronegativity difference related to chemical disorder. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363804
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