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  • 1
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    Spacing and amplitude of IR temperature anomalies and hydrate content of sediments from ODP Leg 304 sites (Table 1) (2004)
    PANGAEA
    In:  Supplement to: Tréhu, Anne M; Long, Philip E; Torres, Marta E; Bohrmann, Gerhard; Rack, Frank R; Collett, Tim S; Goldberg, D S; Milkov, Alexei V; Riedel, Michael; Schultheiss, P; Bangs, N L; Barr, Samantha R; Borowski, Walter S; Claypool, George E; Delwiche, Mark E; Dickens, Gerald Roy; Gràcia, Eulàlia; Guerin, Gilles; Holland, M; Johnson, J E; Lee, Young-Joo; Liu, C-S; Su, Xin; Teichert, Barbara M A; Tomaru, Hitoshi; Vanneste, M; Watanabe, Mahito; Weinberger, J L (2004): Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204. Earth and Planetary Science Letters, 222(3-4), 845-862, https://doi.org/10.1016/j.epsl.2004.03.035
    Details
    Publication Date: 2024-01-09
    Description: Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30–40% of pore space or 20–26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally 〈2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones ~10 m thick, and may occur in up to ~20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change.
    Keywords: 204-1244B; 204-1244C; 204-1244E; 204-1245A; 204-1245B; 204-1245C; 204-1246A; 204-1246B; 204-1247A; 204-1247B; 204-1248A; 204-1248C; 204-1249A; 204-1249F; 204-1250A; 204-1250C; 204-1250D; 204-1251A; 204-1251B; 204-1251D; 204-1252A; Calculated; Comment; Comment 2 (continued); Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; DRILL; Drilling/drill rig; Elevation of event; Event label; Hydrate; Joides Resolution; Latitude of event; Leg204; Length, difference; Longitude of event; North Pacific Ocean; Number; Ocean Drilling Program; ODP; Recovery; Spacing; Temperature, difference
    Type: Dataset
    Format: text/tab-separated-values, 194 data points
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    DATA PANGAEA
  • 2
    Electronic Resource
    Electronic Resource
    Electrical characterization of molecular beam epitaxial GaAs with peak electron mobilities up to ≈4×105 cm2 V−1 s−1 (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 478-480 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of varying the temperature (Tcr) of an As4→As2 cracker furnace between 600 and 700 °C on the properties of GaAs grown by molecular beam epitaxy has been evaluated using 4–300 K Hall measurements and 4.2 K far-infrared photoconduction spectroscopy, in an extension of earlier work on high-mobility material (Ref. 1). The residual donors are silicon and sulphur with mid-1013 cm−3 concentrations under As2-growth conditions (Tcr=700 °C). By lowering Tcr, the silicon concentration is reduced substantially, leaving sulphur as the principal impurity. A 15-μm-thick layer grown with Tcr=650 °C has measured free-electron densities of ≈2.8×1013 cm−3 and peak mobilities ≈4×105 cm2 V−1 s−1 at ≈28–42 K, the highest ever recorded in bulk GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104613
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  • 3
    Electronic Resource
    Electronic Resource
    Nanolithography with an atomic force microscope for integrated fabrication of quantum electronic devices (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1775-1777 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a novel technique using an atomic force microscope (AFM) for integrated nanometer-scale lithography on various mask materials such as photoresist or gold covering a mesa-etched GaAs-AlGaAs heterostructure at ambient conditions. The generated patterns can be transferred to the two-dimensional electron gas by wet chemical etching or by ion beam irradiation. We succeed in fabricating hole arrays with a periodicity down to 35 nm and a hole diameter of only a few nanometers. In magnetoresistance studies on so-called antidot devices with 95 nm period at T=4.2 K we can clearly observe commensurability oscillations, demonstrating the successful pattern transfer to the electron system. With the AFM we can also pattern lines of varying width and depth into prefabricated devices. © 1994 American Institue of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112914
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  • 4
    Electronic Resource
    Electronic Resource
    New electroabsorptive device with negative resistance based on a low-responsivity GaAs/AlAs multiple quantum well (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1117-1119 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose and demonstrate a novel electroabsorptive device which possesses N-type negative resistance. The device consists of a low responsivity GaAs/AlAs multiple quantum well modulator on top of a GaAlAs photodetector. The structure has a larger photocurrent contrast ratio in the negative resistance region (∼3:1 as the voltage changes from 0 to 15 V) than conventional self-electro-optic effect devices (SEEDs). The characteristics of the device change only a little up to high illumination levels (2 mW continuous wave in a 2.8 μm/1e2 diameter spot). We discuss the possible applications of this element as an improved bistable reflection-mode SEED and as an optically controlled microwave oscillator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110824
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  • 5
    Electronic Resource
    Electronic Resource
    Far-infrared photocurrent of quantum wires (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2270-2272 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the photocurrent of quantum capacitor devices consisting of an electron wire array induced in an undoped AlAs/GaAs heterojunction with an interdigitated gate electrode. The photocurrent measures the collective one-dimensional intersubband resonance in the electron wires. The new technique to measure fundamental excitations of nanostructured electron systems yields strong signals even at very low electron densities so that only a single one-dimensional subband is occupied. Compared to previous far-infrared transmission studies the length and the number of the wires averaged in our technique is substantially smaller. The intersubband resonance in our devices is tunable in a wide range of energies up to 10.5 meV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111983
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  • 6
    Electronic Resource
    Electronic Resource
    Single electron charging at temperatures above 4 K in ultrasmall lateral quantum dots patterned on shallow GaAs/AlGaAs heterostructures (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3666-3668 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate single electron charging in fully controllable nanoscale quantum devices at temperatures above 4 K. Hitherto, single electron devices operating at "high'' temperatures have been two-terminal, having no control electrode, whereas fully tunable structures such as quantum dots have only shown charging effects at temperatures of 4 K or less. We have fabricated ultrasmall quantum dots on modulation doped heterostructures where the two-dimensional electron gas is less than 30 nm from the surface. Dots with lithographic diameter 150 nm show Coulomb oscillations up to temperatures of 7 K. Higher temperature operation allows potential applications to be considered without the need, for example, of a dilution fridge. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114134
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  • 7
    Electronic Resource
    Electronic Resource
    X-ray reciprocal space mapping of GaAs/AlAs quantum wires and quantum dots (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 947-949 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Periodic arrays of 150 and 175 nm-wide GaAs–AlAs quantum wires and quantum dots were investigated, fabricated by electron beam lithography, and SiCl4/O2 reactive ion etching, by means of reciprocal space mapping using triple axis x-ray diffractometry. From the x-ray data the lateral periodicity of wires and dots, and the etch depth are extracted. The reciprocal space maps reveal that after the fabrication process the lattice constant along the growth direction slightly increases for the wires and even more so for the dots. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113606
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  • 8
    Electronic Resource
    Electronic Resource
    Improvements in strain-balanced InGaAs/GaAs optical modulators for 1047-nm operation (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1192-1194 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a self-electro-optic effect device (SEED) designed to work at 1047 nm to match the high power available from a Nd:YLF laser. The device uses a strain-balanced InGaAs/GaAs multiple quantum well grown on a GaAs substrate with an InGaAs buffer layer of linearly graded composition. It has improved performance compared to previous devices in this system. We have obtained a single pass modulation contrast ratio of 1.74 by applying 13-V reverse bias, and have found 99% photodetection quantum efficiency under the built-in junction field. Bistability in a resistor-SEED configuration is demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110886
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  • 9
    Electronic Resource
    Electronic Resource
    Model for conductance in dry-etch damaged n-GaAs structures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2335-2337 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model for the effects of dry-etch damage on the conductances of etched structures is developed. Expressions for defect distribution are obtained for top-surface and sidewall damage. The expression for sidewall damage is used in the calculation of wire conductances. The model accounts accurately for changes in experimentally measured conductances of SiCl4-etched n+-GaAs wires with variations in material carrier concentration, epilayer thickness, and etch time/depth. The analysis indicates that defects are created at a significant rate at sidewalls as compared to top surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108235
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  • 10
    Electronic Resource
    Electronic Resource
    1.2 K Shubnikov–de Haas measurements and self-consistent calculation of silicon spreading in δ- and slab-doped In0.53Ga0.47As grown by molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 940-942 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetotransport measurements are reported for In0.53Ga0.47As layers grown by molecular beam epitaxy (MBE) at different substrate temperatures (Ts) and either δ- or slab-doped with Si. Multiple subband densities deduced from the Fourier analysis of 1.2 K Shubnikov–de Haas measurements are compared with those derived from self-consistent calculations which include nonparabolicity and the doping profile width wSi as a fitting parameter. Significant spreading of the Si donors away from the doping plane is deduced for deposition at Ts≈520 °C, while no measurable migration is inferred for Ts≤470 °C, leading to near-ideal δ-doping behavior. Contrary to previous results [McElhinney et al., J. Cryst. Growth 150, 266 (1995)], no evidence for amphoteric behavior has been found for Si areal densities up to 4×1012 cm−2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116105
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