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  • 1
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    A 3-D model to analyze environmental effects of dredging operations – application to the Port of Marin, Spain (2014)
    Copernicus
    Details
    Publication Date: 2014-04-01
    Description: Historically, the study of dredging processes has depended on physical laboratory tests. The IH-Dredge model has been developed to simulate these processes numerically. It simulates the evolution of the seabed, sediment and toxic substances involved in dredging operations. The model has been calibrated and validated with experimental data, and it has been applied in a dredging operation in the Port of Marin, Spain.
    Print ISSN: 1680-7340
    Electronic ISSN: 1680-7359
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 2
    Electronic Resource
    Electronic Resource
    Electron transverse energy distribution in GaAs negative electron affinity cathodes: Calculations compared to experiments (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1809-1815 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transverse momentum of photoelectrons released from a negative electron affinity GaAs cathode is small compared with other thermonic or field emission electron sources. A low photoelectron transverse momentum in vacuum promises highly focused, low-energy beams useful for numerous applications. A simplified theory for electron emission from GaAs predicts much lower electron transverse momentum than those previously measured experimentally. To address this theory–experiment mismatch, Monte Carlo based calculations were compared with experimental data. We checked the possibility of there being electron scattering in the Cs,O layer; however, none of the scattering checked (isotropically distributed, cosine distributed, and Rutherford scattering) properly fit the experimental results. The assumption of conservation of the parallel component of the crystal momentum k during the emission is mainly believed to be responsible for the calculation-theory disagreement. The best simulation-experiment fit was obtained through a relaxation of the conditions imposed on the transverse momentum inside and outside of the semiconductor when an ideal interface is considered. We obtained the best results by assuming that the effective mass of the electron inside GaAs is equal to the effective mass of the electron in vacuum. Two independent experiments confirmed that in both cases, this same-mass approximation gives the best fit. The physical meaning of this is not clear, but it seems to be related to the amorphous nature of the Cs,O layer. We conclude that the way to get lower electron transverse energy spread cathodes is to study alternative activation methods and new materials with smaller effective electron masses. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362992
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  • 3
    Electronic Resource
    Electronic Resource
    Physics of high-intensity nanosecond electron source: Charge limit phenomenon in GaAs photocathodes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7318-7323 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs negative electron affinity cathodes are used as high-intensity, short-time electron source at the Stanford Linear Accelerator Center. When the cathodes are illuminated with high-intensity laser pulses draw peak currents that are extremely high, typically of tens of Amperes. Because of the high currents, some nonlinear effects are present. Very noticeable is the so-called charge limit (CL) effect, which consists of a limit on the total charge in each pulse; that is, the total bunch charge stops increasing as the light pulse intensity increases. The CL effect is directly related to a photovoltage built up in the surface as a consequence of the photoelectrons coming from the bulk. We discuss possible ways to minimize the formation of the surface photovoltage. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361448
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  • 4
    Electronic Resource
    Electronic Resource
    Photoemission from the Sr/Si(001) interface (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6070-6072 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of Sr on n-type Si(001) was studied in detail for coverages between 0 and 1 monolayer (ML) using core level photoemission spectroscopy. In a similar manner, the Sr saturation coverage was studied in the 600–925 °C temperature range. Data analysis was carried out by a method that allows accurate determination of the band-bending shifts. Using this method it is possible to pinpoint the formation and destruction of chemical species from bungled core level photoemission data without needing to know details of the chemical composition of the spectra. Through this analysis it was established that the interaction between Sr and Si breaks down the binding energy difference between upward and downward Si dimer atoms. In addition, it was found that the saturation coverage exhibits a clear plateau at 1 ML around 650 °C, and a slope change at 1/3 ML around 850 °C. The surface band bending suffers a discontinuous increase as the Sr coverage surpasses 〈fraction SHAPE="CASE"〉12 ML and as the low energy electron diffraction symmetry changes from [2×3] to [2×1]. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415758
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  • 5
    Electronic Resource
    Electronic Resource
    Trapping characteristics of Te-related centers in GaAs1−xPx (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 5295-5301 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transient capacitance and photocapacitance techniques have been used to study the characteristics of two electron traps related to Te in GaAs1−xPx: Te. Levels En1 and En2 have thermal activation energies of 0.17 and 0.27 eV, respectively, and their thermal electron emission and capture rates deviate markedly from Schockley–Read–Hall theory for near band gap crossover compositions. Such centers are found for 0.3〈x≤1, are linked to the X conduction band minima, and their photoionization thresholds are 0.5 and 1 eV, respectively. Trap concentrations have been studied as a function of Te doping level, Zn diffusion temperature, and N content (x〉0.4) in GaAsP LEDs. It is suggested that both defects belong to the DX type, and they have been described by a large lattice relaxation model. Franck–Condon energies of 0.3 and 0.95 eV have been determined, respectively. The properties of present Te-related defects are quite similar to donor related centers in AlxGa1−xAs, including the nonexponential capacitance transients found in near x∼0.4 compositions. It is important to mention that both centers have very large hole capture coefficients (σp〉10−14 cm2) and behave as efficient recombination centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335484
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis of the water bound to a polymer matrix by infrared spectroscopy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5431-5437 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article focuses on the interaction of water with solid polymers. A portion of the water adsorbed in hydrophilic materials is strongly bound to individual sites (bound water), while an additional amount is bound less firmly to the polymeric chain (free water). Both free and bound water have been the subject of many studies that have uncovered, in some cases, qualitative evidence of the presence of water directly bound. In this article, we report a method to determine the different fractions of water adsorbed in hydrophilic materials. One fraction corresponds to the first layer in contact with the adsorbing solid and the other corresponds to the remaining water absorbed layers. We were able to determine said quantification by means of measuring the change in the natural vibration frequency brought about by the interaction of water molecules with the solid. The measurement was done on films of methylcellulose exposed to humid environments using infrared spectroscopy and gravimetric static microclime sorption methods. Theoretical predictions for bound water were developed using multilayer adsorption models. The experimental concentration of bound water as a function of relative humidity was compared with these predictions, allowing us to judge the applicability of different adsorption models employed in the study of gas condensation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1365427
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  • 7
    Electronic Resource
    Electronic Resource
    Centers at junction boundaries in AlGaAs single heterojunction red light-emitting diodes (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2235-2243 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In AlGaAs red light-emitting diodes fabricated by liquid-phase epitaxy the presence and characteristics of deep centers located near the injecting-active junction boundaries have been studied. Transient capacitance, DLTS, photocapacitance, and photocurrent techniques have been applied. Besides the presence, in the n-type injecting layer, of centers related to the Te dopant (DX defects), deep hole traps have been detected at both sides of the n-p heterojunction. The physical origin of such hole traps, present in moderately large concentrations, is discussed in terms of Zn-related complexes. This defect pattern allows us to explain the thermal- and photocapacitance, and the freeze-out and photocurrent characteristics found in such devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336365
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  • 8
    Electronic Resource
    Electronic Resource
    Novel method to determine capture cross-section activation energies by deep-level transient spectroscopy techniques (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 660-661 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep-center characterization by deep-level transient spectroscopy (DLTS) allows a direct determination of the trap thermal emission activation energy. However, capture barrier energy measurements, based on trap partial filling by pulses of increasing width, require a quite different experimental processing and pose some hardware difficulties. In this letter we present a new method to determine the trap capture barrier energy, one that requires constant-width filling pulses and obtains capture information from standard DLTS data. This technique has been applied to Te-, Sn-, and Si-related DX centers in AlGaAs alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99366
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  • 9
    Electronic Resource
    Electronic Resource
    Direct evidence of the DX center link to the L-conduction-band minimum in GaAlAs (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 383-385 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrostatic pressure techniques together with deep level transient spectroscopy (DLTS) measurements have shown that the Si-DX center in GaAlAs is linked to the L-conduction-band minimum. When hydrostatic pressure is applied to a 74% Al content sample, an exponential reduction of the DLTS signal is observed. This exponential dependence with pressure arises from the reduction of the DX filling factor (electron occupancy) due to the increasing X-L energy difference with pressure. Our results, together with previous data, also show that the capture barrier height originating from the lattice relaxation is an intrinsic parameter of both the material and the donor species, that does not depend on Al content or conduction-band structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99473
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of the local environment on the properties of DX centers in Si-doped GaAs and dilute AlxGa1−xAs alloys (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 934-936 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si-doped GaAs and dilute AlxGa1−xAs alloys under hydrostatic pressure have been studied using deep level transient spectroscopy (DLTS). In GaAs the DLTS spectrum of the DX center is a single peak. In AlGaAs however, multiple peaks, resulting from different thermal emission rates from donors having different numbers of Al atoms as near neighbors, are observed. The pressure dependence of the electron occupation of individual DX levels shows that the larger the number of Al atoms near the Si donor, the lower the energy position of the DX level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102630
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