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  • American Institute of Physics (AIP)  (80)
  • 2005-2009
  • 1990-1994  (80)
  • 1945-1949
  • 1940-1944
  • 1
    Electronic Resource
    Electronic Resource
    Room- and low-temperature assessment of pseudomorphic AlGaAs/InGaAs/GaAs high-electron-mobility transistor structures by photoluminescence spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5931-5944 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of room- and low-temperature photoluminescence (PL) spectroscopy for the assessment of n-type pseudomorphic AlGaAs/InGaAs/GaAs high-electron-mobility transistor structures is reported. We describe a method to determine the InAs mole fraction x, the channel layer thickness L, and the confined two-dimensional electron gas density (ns), based on the comparison between the PL transitions and the recombination energies derived from self-consistent calculations of the subband structure. A detailed analysis of the optical transitions and their dependence on the Fermi level position and temperature is performed. It is shown that, in real devices, the high sensitivity of the recombination energies and intensities on small changes of the parameters x, L, and ns allows us to detect deviations from their nominal structural parameters within the uncertainty of the molecular beam epitaxy growth technique. The present assessment procedure has been applied to a significant number of samples, and it has been backed by independent measurements of these parameters by more sophisticated techniques such as Shubnikov–de Haas and PL excitation in standard and gated samples, and by physical techniques like transmission electron microscopy and Auger spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358416
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  • 2
    Electronic Resource
    Electronic Resource
    Liquid EXAFS cells for measurements in transmission and fluorescence mode of corrosive samples (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2153-2154 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design of two small, compact and portable cells for EXAFS measurements of liquids is presented. One of the cells has been optimized for transmission measurements and the other for fluorescence. The sample chamber of both cells has been designed metal free to avoid corrosion by acids or bases. Materials and construction of the cell are such that their cost is quite low. The cells have been tested by recording EXAFS spectra of ionic aqueous solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144718
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  • 3
    Electronic Resource
    Electronic Resource
    Enhanced carrier densities and device performance in piezoelectric pseudomorphic high-electron mobility transistor structures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1072-1074 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The addition of a piezoelectric field in AlGaAs/InGaAs/GaAs HEMT structures is shown to lead to enhanced electron densities and hence improved device performance. Growth of a strained InxGa1−xAs layer is in [111]A direction causes a piezoelectric field to be built into the quantum well of a pseudomorphic HEMT, which opposes the electric field due to charge transfer and hence lowers the confinement energy. This leads to carrier densities 50% larger than in equivalent [100] structures, with the wave function also spaced further away from the dopant impurities and the well interfaces. We expect these factors to give improved device performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107694
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  • 4
    Electronic Resource
    Electronic Resource
    Pyrite thin films: Improvements in their optical and electrical properties by annealing at different temperatures in a sulfur atmosphere (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4551-4556 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Iron pyrite thin films prepared by flash evaporation of pyrite powder have been annealed at different temperatures in a sulfur atmosphere. We present some results on the influence of the annealing temperature (from 250 to 450 °C) on the optical and electrical properties of three groups of samples with different thicknesses ((approximately-equal-to)0.3, 0.6, and 1 μm, respectively). Sulfuration temperature has a clear influence on the optical absorption and electrical resistivity of the films, with some differences in their behavior depending on the film thickness. In light of the available present knowledge of pyrite thin films, interpretation of the obtained results is difficult, it suggests that the shape of the optical absorption curves (and their absorption edge) at low photon energies is determined by the density of point defects, which decreases on increasing the annealing temperature. On the other hand, the electrical resistivity seems to be influenced by both the film grain size and point defect density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354373
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal diffusivity measurements on solids using collinear mirage detection (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1539-1547 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A report on the adequacy of the collinear mirage technique for thermal diffusivity measurements on bulk homogeneous solids is presented. A 3D theoretical model for collinear deflection has been developed from which two simple linear relations between measurable parameters and the thermal diffusivity have been obtained. Two methods, the so-called zero-crossing and phase methods, are discussed in detail. The second one seems to be a promising tool for thermal diffusivity determination. It has been validated by means of experimental measurements on a set of samples with known thermal diffusivities. The technique is restricted to semitransparent solids but is also valid for materials with either high or low thermal diffusivities, being specially useful for this last group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354854
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  • 6
    Electronic Resource
    Electronic Resource
    Slit morphology of electromigration induced open circuit failures in fine line conductors (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3201-3203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed transmission and scanning electron microscopic images of electromigration-induced open circuit failures are presented for fine line aluminum alloy thin film interconnects. A characteristic slit open circuit, similar to stress migration open circuits in narrow interconnects, is shown for various film compositions, processing, and deposition conditions. It is suggested that slit failure morphology is more generally observed for low (≈1) ratios of conductor line width to film grain size. The slit failures observed often occur near copper rich precipitates. The morphology of several slit voids suggests that they are transgranular across the linewidth, consistent with other recent reports of electromigration induced damage in single crystal interconnects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351484
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of the transient spectral density of velocity fluctuations in GaAs and InP (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2322-2330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a multiparticle Monte Carlo method, a theoretical analysis of the spectral density of velocity fluctuations in semiconductors has been performed, under both stationary and transient conditions (when the electric field applied to a semiconductor changes). In the case of the transient analysis a general method has been developed and applied to N-type GaAs and InP. The results obtained are interpreted in terms of the microscopic processes occurring during the transient. Significant differences between these materials have been observed. The following results were found: (i) The main source of noise is the presence of carriers in the Γ valley subject to the action of high fields, and the velocity-disorienting effect of the intervalley mechanisms; (ii) the maximum in the spectral density is essentially due to the presence of intervalley mechanisms; (iii) the dominant frequencies in the spectral density are strongly affected by the duration of the free flights; (iv) for long times, the transient spectral density converges on the steady-state one of the final field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351574
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  • 8
    Electronic Resource
    Electronic Resource
    Photothermal detection and characterization of a horizontal buried slab by the mirage technique (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3031-3037 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a theoretical and experimental analysis of the mirage detection and measurement of a semi-infinite horizontal buried slab of air within opaque solids. A detailed study on the effects introduced by the mirage parameters (pump and probe beam sizes, probe beam height) as well as by the surface features is discussed. We use pump and probe beams orthogonally superimposed, and detection is made of the amplitude and phase of the normal component of the mirage deflection. Air slabs with a thickness (e2) as low as 0.1 μm and located down to a depth (e1) of 0.3(square root of)ks (ks is the thermal diffusivity of the material) can be easily observed. Detection improves as the pump radius (a) and probe height (z0) increase, although a compromise is necessary because of signal attenuation. Determination of e1 and e2 through the model fitting, requires an independent control of a and z0. The use of low frequencies avoids the effects of surface features on the slab detection. However, for surface planar horizontal steps, their height must be incorporated into the model as a variation of z0 in order to characterize the slab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349334
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of a parasite hybridizer on the magnetic behavior of partially delocalized transition shell systems (abstract) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5812-5812 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated how the behavior of a transition shell atomic species (species A) with orbital magnetism, driven by hybridization-mediated interactions via a sea of band electrons, is modified by the addition of a second parasite hybridizer (species B). Our approach involves a two-stage procedure. First, we calculate the modification of the band electron sea by hybridization with B by using a slave boson formalism. Second, the modifications in the A-A interionic interactions driving the orbital magnetic ordering are calculated by applying a Schrieffer–Wolff transformation on the renormalized Anderson lattice hamiltonian obtained from the first stage. The new A-A interactions have a different radial dependence (range factor) which depends in a nonlinear way on the band-B hybridization strength: and the consequences of this change on the magnetic ordering are studied using a mean-field approximation. This enables us to model the reduction in the magnetic ordering caused by competing parasite hybridization, and the dependence of this reduction on the relative hybridization strengths of the two species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350119
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical critical-state susceptibility spectra and their application to high-Tc superconductors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5463-5477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fundamental complex susceptibilities χ=χ'−jχ‘ are calculated from the symmetric critical-state hysteresis loops M(H) for an infinitely long hard superconductor with a rectangular cross section 2a×2b (a≤b). For the critical-state model, the Bean, the Kim, the exponential law, and the triangular-pulse local-internal-field-dependent critical-current densities Jc(Hi) are chosen. The results of χ' and χ‘ are given as functions of the field amplitude Hm normalized to the full-penetration field Hp, the sample dimensional ratio a/b, and the p parameter that characterizes the Hi nonuniformity in the sample at H = Hp on the initial M(H) curve. χ‘(−χ') curves are also given for the different functional Jc(Hi) and other conditions. These theoretical critical-state susceptibilities are particularly useful in the study of sintered high-Tc superconductors. For these materials, the procedures to determine the effective grain volume fraction f*g and the averaged and the local intergranular critical-current densities 〈Jc〉acs and Jc(Hi) by means of ac susceptibility measurements using such theoretical critical-state-susceptibility functions are described. Related problems met in the high-Tc superconductor study such as sample performance nonuniformity, frequency dependence, grain clusters, and susceptibilities for the grains are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350204
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