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  • 2015-2019  (557)
  • 1990-1994  (147)
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  • 1
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    Facies evolution of nearshore marine clastic deposits during the Tortonian transgression—Granada Basin, Betic Cordilleras, Spain (1991)
    Elsevier
    Details
    Publication Date: 1991-04-01
    Print ISSN: 0037-0738
    Electronic ISSN: 1879-0968
    Topics: Geosciences
    Published by Elsevier
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    PAPER CURRENT
  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Electron distribution in pseudomorphic Al0.30Ga0.70As/ In0.15Ga0.85As/GaAs δ-doped heterostructures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1161-1168 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the electronic properties of the δ-modulation-doped Al0.30Ga0.70As/In0.15Ga0.85As heterojunction for a variety of different configurations. Experimental findings are compared with theoretical predictions based on the two-band effective mass approximation including strain, many-body, finite temperature, and DX center effects. We have also examined the case where the δ doping is placed in an embedded GaAs well within the Al0.30Ga0.70As. This is intended to reduce the effects of DX centers. In this instance, as the doping concentration is increased, experimentally determined channel density, ns, suggests higher saturation values, which may leave a residual electron density in the GaAs well. This residual charge density is parallel with the electron density in the InGaAs well and represents an additional conducting path. The features of the theoretical channel density versus doping density curves are confirmed by 300 and 1.6 K resistivity and Hall measurements, and Shubnikov–de Haas measurements made at 1.6 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354916
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Thermal diffusivity measurements in solids by the "mirage'' technique: Experimental results (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1216-1223 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work provides the experimental confirmation of a generalized theory for thermal diffusivity measurements of solid samples using the "mirage'' technique presented by the authors in a previous paper [A. Salazar, A. Sanchez-Lavega, and J. Fernandez, J. Appl. Phys. 65, 4150 (1989)]. Moreover the influence of different effects on such determinations has been analyzed, and the limits of validity of the method have been established. The most important influence relies on the finite nature of two parameters: the height of the probe beam above the sample surface h and the radius of the exciting beam a. Such effects in all solids are discussed in detail according to their bulk thermo-optical properties and for two ways of measuring: "bouncing'' (probe beam sent to the sample surface at a small angle) and "skimming'' (probe beam parallel and grazing the surface). The first way of measuring gives reliable results while the second one must be managed with care. In any case, significant shifts in the thermal diffusivity measurement for nonzero values of h and a are specially observed when the thermal diffusivity of the sample is much lower than that of the deflecting medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347306
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  • 6
    Electronic Resource
    Electronic Resource
    Electrical resistivity between 10 and 1000 K of ferromagnetic Co75Si25−xBx and Co100−x(Si0.6B0.4)x amorphous ribbons (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4610-4616 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The study of the variation of the electrical resistivity ρ between 10 and 1000 K has been performed in the Co75Si25−xBx and Co100−x(Si0.6B0.4)x ferromagnetic amorphous series. A general analysis of the curves gives useful data about the main features of ρ in these materials: Curie temperatures Tc, temperatures of the minima Tmin, crystallization temperatures Tx, temperature coefficient of resistivity, and absolute resistivity. The correlations between these magnitudes have been discussed including direct comparison with the nonmagnetic Ni-Si-B similar compounds. An analysis of the structural and magnetic contributions to the resistivity is presented in the whole temperature range. The structural part is interpreted in the framework of the extended Ziman model and it is superposed on the magnetic term. A T2 magnetic contribution coming from the spin wave scattering is found at temperatures between Tmin and approximately 0.5 Tc. At higher temperatures, the magnetic part seems to be understood taking into account the mean field approximation. Saturation magnetization M(T) measurements over 300 K were carried out in order to get an experimental hint of the correlation between the magnetic ρ and M(T) with rather satisfactory results. Besides the general analysis we report the achievement of a progressive shift of Tmin in some compounds (in particular in Co70Si18B12) in which a tentative explanation might be based on phonon ineffectiveness arguments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346170
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  • 7
    Electronic Resource
    Electronic Resource
    Enhancement of the localized behavior in CeNi0.8Pt0.2 Kondo compound replacing Ce by magnetic ions (Pr,Nd) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6118-6120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The substitution of Ce by magnetic ions such as Pr or Nd in the CeNi0.8Pt0.2 Kondo ferromagnetic compound not only favors the magnetic interactions increasing the Curie temperatures, but also disturbs the coherence of the Kondo lattice state leading to a decrease of the Kondo temperatures and an increase of the Ce intrinsic magnetic moment. These effects have been studied by resistivity, magnetization, and neutron diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358325
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  • 8
    Electronic Resource
    Electronic Resource
    Strain relaxation of compositionally graded InxGa1−xAs buffer layers for modulation-doped In0.3Ga0.7As/In0.29Al0.71As heterostructures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1129-1131 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Modulation-doped In0.3Ga0.7As/In0.29Al0.71As heterostructures have been grown on GaAs substrates by molecular beam epitaxy using a compositionally step-graded InxGa1−xAs buffer layer. We found that the buffer layer produces essentially total relaxation with 〈2×106/cm2 dislocations present in the In0.3Ga0.7As layer. The structural perfection of this layer is reflected in the electrical and galvanomagnetic properties of its two-dimensional electron-gas channel which has a sheet-electron density of 1.2×1012/cm2, peak mobilities of 9 300 cm2/V s at room temperature and 31 000 cm2/V s at 77 K, and a mobility anisotropy of ∼4% along orthogonal 〈110〉 directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106429
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  • 9
    Electronic Resource
    Electronic Resource
    Reflection high-energy electron diffraction intensity oscillations of germanium growth on Si(100) using gas source molecular beam epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3066-3068 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflection high-energy electron diffraction intensity oscillations during Ge heteroepitaxy on Si(100) have been observed using a gas source molecular beam epitaxy system. Intensity oscillations can be observed over 6 ML (monolayers) of growth in the temperature range 400–650 °C. The oscillation frequency, however, varies from the first to subsequent layers and this variation is interpreted primarily as a change in the limiting growth kinetics as the surface composition changes from Si to Ge. Growth temperature and GeH4 flux dependence data indicate that the surface Ge concentration increases gradually, not abruptly, over the first several layers of deposition. Surface roughening effects which are attributed to Stranski–Krastanov type growth, are also found to contribute to the nonuniform oscillation frequency. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112508
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  • 10
    Electronic Resource
    Electronic Resource
    Composition dependent transport properties of strain relaxed InxGa1−xAs(x〈0.45) epilayers (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1116-1118 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The concentration and mobility of the two-dimensional electron gas present at the interface between strain-relaxed, lattice matched, InyAl1−yAs/InxGa1−xAs(x 〈 0.45), modulation doped heterojunctions grown by means of compositionally step-graded buffer layers on GaAs substrates, were measured at room temperature and at 77 K. The composition dependence of the electron density is attributed to the dependence of the band-gap energy of InxGa1−xAs and that of InyAl1−yAs on x, with a conduction band offset, ΔEc∼0.67ΔEg. The room temperature electron mobility increases from 9×103 cm2/V s for x=0.07 to 1.05×104 cm2/V s for x=0.45. Such strain-relaxed heterostructures have higher electron mobilities than similar pseudomorphic structures with the same sheet electron concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107686
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