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  • 1990-1994  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Transmission electron microscopy and transmission electron diffraction structural studies of heteroepitaxial InAsySb1−y molecular-beam epitaxial layers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 8227-8236 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular-beam epitaxy InAsySb1−y layers were grown at temperatures ranging from 295 to 470 °C across the full composition range. Transmission electron microscopy and transmission electron diffraction (TED) examinations showed that for layers grown at and below 400 °C with nominal compositions 0.4〈y〈0.8, separation into two phases occurred resulting in a series of alternating plates approximately parallel to the layer surface. TED showed that the cubic lattices of the two phases were tetragonally distorted and their compositions were deduced to be typically InAs0.38Sb0.62 and InAs0.72Sb0.28. The plates were larger and more regular along the [1¯10] direction than the [110] direction. As the growth temperature increased from 295 to 400 °C, for layers of nominal composition InAs0.5Sb0.5, the plate length increased from 0.1 to 2.0 μm and the plate thickness from 10 to 50 nm. Crystallographic defects were present in the layers and their occurrence was different in the phase-separated and non-phase-separated layers. The plates formed spontaneously at the growing surface and were stable during subsequent annealing at 350 and 370 °C. It is suggested that they arise due to the presence of a miscibility gap at these growth temperatures. We have termed these spontaneously grown plate structures "natural'' strained layer superlattices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353440
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  • 2
    Electronic Resource
    Electronic Resource
    Atomic ordering in molecular beam epitaxial InAsySb1−y natural strained layer superlattices and homogeneous layers (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3593-3595 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscope studies were made of CuPt-type ordering in molecular beam epitaxial InAsySb1−y natural strained layer superlattices and homogeneous layers grown at temperatures in the range 295–470 °C. Ordering occurs with a maximum at a growth temperature of 370–400 °C, individual (1¯11) and (11¯1) ordered domains up to 10 nm in size are present, and there is a modulation of periodicity 3 d110 within the layers, where d110 is the (110) lattice spacing. The latter correlates with a [2×3] atomic surface reconstruction present during growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111208
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxial growth of high quality InSb (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3338-3340 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter we report on the growth of high quality InSb by molecular beam epitaxy that has been optimized using reflection high energy electron diffraction. A 4.8 μm InSb layer grown on GaAs at a growth temperature of 395 °C and a III/V incorporation ratio of 1:1.2 had an x-ray rocking curve of 158 arcsec and a Hall mobility of 92 300 cm2 V−1 at 77 K. This is the best material quality obtained for InSb nucleated directly onto GaAs reported to date. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112384
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxial growth of InAsSb strained layer superlattices. Can nature do it better? (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3324-3326 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular beam epitaxial growth of a normally homogeneous InAs0.5Sb0.5 alloy below 430 °C results in its coherent phase separation into platelets of two different alloy compositions with tetragonally distorted crystal lattices. This produces a "natural'' strained layer superlattice (n-SLS) with clearly defined interfaces modulated in the [001] growth direction. A description of the n-SLS growth mode in InAsSb is outlined, and the optical response of a n-SLS structure, which extends to 12.5 μm−considerably further than that of a homogeneous InAs0.5Sb0.5 layer (8.9 μm)−is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105720
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  • 5
    Electronic Resource
    Electronic Resource
    Passive mode locking and Q switching of an erbium 3 μm laser using thin InAs epilayers grown by molecular beam epitaxy (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1658-1660 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Passive mode locking and Q switching has been achieved for the first time in an Er3+:YSGG laser at λ=2.8 μm using ultrathin single-crystal InAs epilayers grown on GaAs substrate which were subsequently bombarded with 15 keV protons at a dose of 1013 cm−2. The bleaching effect was due to a dynamic Moss–Burstein mechanism with a fast (〈100 ps) recovery time. In the case of passive mode locking, pulses of 10 MW power were generated at λ=2.8 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106259
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  • 6
    Electronic Resource
    Electronic Resource
    Electromagnetic Mode Conversion By Surface-Conductivity Anomalies: Applications For Conductivity Soundings (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 117 (1994), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A natural-source electromagnetic sounding of the earth made near a surface conductivity anomaly will resolve different features of the underlying conductivity structure than a sounding in a more uniform region. the surface-conductivity anomaly deflects horizontal electric currents induced by an external source into a vertical plane converting transverse-electric (TE) mode currents into the transverse (TM) mode. the resulting current distribution involves both vertical current flow and spatial variations with shorter wavelengths than the external field, providing increased resolution of resistive layers and of the conductivity structure at shallow depths. We exmine the sensitivity of the converted-mode response for the vertical-gradient sounding (VGS) method in order to plan electromagnetic soundings in a narrow ocean strait such as the Strait of Georgia between Vancouver Island and the Canadian mainland.An integral-equation method is used to model the current system induced by a mode converter, consisting of a known conductivity structure, such as a body of ocean water. It is shown that the depth of penetration of the secondary current distribution produced by the mode converter depends on both the horizontal scale of the feature and the distance from its edge. Within this depth range the current system is strongly perturbed by the existence of either conductive or resistive layers. the sensitivity of the VGS response (the ratio of the horizontal magnetic field at the base and surface of the mode converter) is examined using forward modelling of layered conductivity structures. the response is found to be dependent on both the TE and TM current systems. For a narrow ocean strait such as the Strait of Georgia, a measurement of the converted-mode VGS response along a line of sites on the floor of the strait, will provide resolution of conductive and resistive layers in the upper 10 km. the appropriate frequency range over which the VGS response should be measured in the strait is 10−2 Hz to 10 Hz.In our investigation of mode conversion we examine both the frequency- and time-domain response. Snap shots showing the current system evolving in the earth after a step or impulse illustrate the interaction of the EM signals with resistive and conductive layers. We show that the time-domain response can be used in a ‘geometrical sounding’analogous to seismic refraction to determine the conductivity structure. Finally we examine the limitations on the accuracy of the frequency and time-domain VGS response imposed by natural signal levels and instrument sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1994.tb03303.x
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  • 7
    Electronic Resource
    Electronic Resource
    Geomagnetic induction in the Tasman Sea and electrical conductivity structure beneath the Tasman Seafloor (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 102 (1990), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: During the Tasman Project of Seafloor Magnetotelluric Exploration recordings were made of the natural magnetic and electric field variations along a line of seafloor sites crossing the Tasman Sea. Using these data and additional magnetic field recordings made on the Australian continent the pattern of geomagnetic induction in the Tasman Sea Region is examined. An investigation of the seafloor magnetotelluric impedance tensor indicates the geomagnetic induction is influenced by the large-scale 3-D conductivity structure of the region. This result is confirmed by a study of impedance estimates obtained using the vertical gradient sounding method (in which the seafloor impedance is determined from the attenuation of the horizontal magnetic field variations through the ocean). Inversion of the E-polarization impedance component from sites in the central Tasman Sea indicates the conductivity structure at depths greater than about 100 km is laterally homogeneous in this region. It is probable that the conductivity structure at these sites includes a high-conducting layer similar to one observed in the Pacific Ocean. One seafloor site, lying on the Tasmantid Seamount Chain, exhibits an increased conductivity at depths of less than 100 km. The increased conductivity may be due to heating of the lithosphere by a hotspot, one proposed source of the seamount chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1990.tb04468.x
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  • 8
    Electronic Resource
    Electronic Resource
    Development and validation of a simple approach to modelling tree shading in agroforestry systems (1992)
    Springer
    Agroforestry systems 20 (1992), S. 243-252 
    Details
    ISSN: 1572-9680
    Keywords: light interception ; agroforestry ; tree shade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There have been a number of models developed which attempt to predict the shading patterns beneath individual tree or forest canopies. We describe a computer-based model which is able to estimate shading patterns through a discontinuous canopy of pruned trees. The model is designed to assist in the layout and management of agroforestry systems with widely spaced trees. The model was tested against data collected from a seven-year-old agroforestry system involving radiata pine, located near Canberra, Australia. The model was shown to slightly but consistently underestimate light penetration at ground level beneath the trees. However, the extent of bias (0.7% to 5%) was so small as to be of little significance in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053142
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