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  • Articles  (420)
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  • 1
    Electronic Resource
    Electronic Resource
    A multichannel monolithic Ge detector system for fluorescence x-ray absorption spectroscopy : The 9th National conference on synchrotron radiation instrumentation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3361-3362 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The construction and performance characteristics of a monolithic quad-pixel Ge detector designed specifically for fluorescence x-ray absorption spectroscopy (XAS) at synchrotron radiation sources is described. The detector semiconductor element has an active surface area of 4.0 cm2 that is electrically separated into four 1.0 cm2 pixels, with little interfacial dead volume. The spatial response of the array demonstrates that cross-talk between adjacent pixels is less than 10% for 5.9-keV photons that fall within 0.5 mm of the pixel boundaries. The detector electronics system utilizes preamplifiers built at LBNL with commercial Tennelec Model TC 244 amplifiers. Employing an 55Fe test source (Mn Kα , 5.9 keV), energy resolution of better than 200 eV is achieved with a 4 msec peaking time. At 0.5 msec peaking time, pulse pileup results in a 75% throughput efficiency for an incoming count rate of 100 kHz. Initial XAS fluorescence measurements at the beamline 4 wiggler end stations at SSRL show that the detector system has several advantages over commercially available x-ray spectrometers for low-concentration counting applications. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146862
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  • 2
    Electronic Resource
    Electronic Resource
    Proper interpretation of photoconductive decay transients in semiconductors having finite surface recombination velocity (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4663-4669 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of finite surface recombination velocity on the proper interpretation of photoconductive decay (PCD) transients in semiconductors is discussed. The limitations of simple analytical equations which relate the observed effective lifetime to the material parameters are considered. It is shown that, under most circumstances, the correct application of the appropriate analytical expression requires some prior knowledge of the material parameters under investigation. Several methods are proposed to extract useful information from PCD experiments. Finally, the practicality of these methods is investigated by measuring the effective lifetimes of high-purity germanium and float-zone silicon using a noncontact PCD technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357304
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  • 3
    Electronic Resource
    Electronic Resource
    Pseudomorphic InyGa1−yAs/GaAs/AlxGa1−xAs single quantum well surface-emitting lasers with integrated 45° beam deflectors (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 7-9 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the first demonstration of pseudomorphic InGaAs single quantum well surface-emitting lasers (SELs), with etched vertical mirrors and integrated 45° beam deflectors fabricated by ion beam etching. 100-μm-wide broad-area SELs exhibited a threshold current of 320 mA, a total power of 126 mW, and a total external differential quantum efficiency of 0.09 W/A for a 500-μm-long cavity. The perpendicular far-field pattern of broad-area SELs showed a full width at half maximum of ∼20°. The lasers with various types of cavities fabricated from the same wafer were compared. Broad-area edge-emitting lasers had a threshold current of 200 mA, a total power of 700 mW, and a total external differential quantum efficiency of 0.52 W/A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104451
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  • 4
    Electronic Resource
    Electronic Resource
    High-power AlGaAs/GaAs single quantum well surface-emitting lasers with integrated 45° beam deflectors (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2048-2050 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on high-power AlGaAs/GaAs graded-index single quantum well surface-emitting lasers (SELs), with etched vertical mirrors and integrated 45° beam deflectors fabricated by a tilted ion beam etching technique. 100-μm-wide, 500-μm-long, broad-area SELs exhibited a threshold current of 300 mA, a peak power of more than 380 mW, and an external differential quantum efficiency of 17% without facet coating. The SELs showed stable operation up to 7th. These results show the highest power and external differential quantum efficiency reported to date for 45° beam deflecting SELs. The full widths at half maximum of the surface-emitting far-field pattern parallel and perpendicular to the laser axis were 8.5° and 14°, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103937
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  • 5
    Electronic Resource
    Electronic Resource
    Ion-implanted extrinsic Ge photodetectors with extended cutoff wavelength (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1431-1433 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Far-infrared properties of a two-layer structure consisting of an ion-implantation doped layer on a thin ultrapure slice of germanium have been studied. Photoresponse extends beyond the shallow impurity absorption edge at 120 μm to about 192 μm. Photoconductivity studies have been performed between 4.2 and 1.3 K. Detectors with an area of 1×1 mm2 have dark currents of less than 100 electrons/s at temperatures ≤1.3 K at a bias of 70 mV. A responsivity of 0.9 A/W and a noise equivalent power of 5×10−16 W/Hz1/2 have been measured using photons in a narrow band 99±0.5 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105189
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  • 6
    Electronic Resource
    Electronic Resource
    Voltage-assisted calorimetric ionization detector (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6858-6860 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new approach to ionizing radiation detection is proposed. The amount of ionization produced in a detector medium is measured by the heat generated as the charged carriers are drifted across the device under an applied voltage. The amount of energy generated can be orders of magnitude larger than that deposited by the radiation itself. A dramatic increase in detector mass can be achieved compared to simple calorimetric particle detectors for equivalent energy thresholds. It is possible to obtain a sensitivity level sufficient for single-carrier detection. The principle of operation has been demonstrated with an experimental device operated at a temperature of 1.8 K, and improved performance is expected at lower temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341976
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  • 7
    Electronic Resource
    Electronic Resource
    Imaging of radio-carbon clusters in high-purity germanium using a self-detection scheme (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3734-3736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new isotope-specific and quantitative technique based on self-detection in a position-sensitive detector has been developed for the imaging of radio-carbon clusters in high-purity Ge. Using a novel position-sensitive detector concept, a one-dimensional spatial resolution of ∼200 μm FWHM and a sensitivity of ∼6×107 14C atoms per cluster has been obtained. This technique can be applied to other semiconductors which can be used to fabricate self-counting position-sensitive nuclear radiation detectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336757
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  • 8
    Electronic Resource
    Electronic Resource
    Electron-hole pair creation at a Ge(100) surface by ground-state neutral Xe atoms (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2213-2215 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have directly measured the excitation of electron-hole pairs at a crystal surface by ground-state neutral atoms. Utilizing seeded molecular beam techniques we have scattered hyperthermal (1–6 eV) Xe atoms from the (100) face of a Ge p-i-n diode and recorded the current transient induced due to the scattering process. We find the product of the excitation and collection probability to be ∼10−4 over a range of kinetic energies 2〈EXe(eV)〈6. The excitation of electron-hole pairs constitutes a small portion of the massive energy loss (ΔE/E∼70%) of the Xe atom to the crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336361
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  • 9
    Electronic Resource
    Electronic Resource
    Single-polarity charge sensing in ionization detectors using coplanar electrodes (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2884-2886 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new method to preferentially sense the collection of single-polarity charge carriers in ionization detectors is presented. It uses coplanar electrodes to closely emulate the function of Frisch grids commonly employed in gas and liquid ionization detectors. The coplanar electrode structure allows for easy implementation on semiconductor detectors. This method can be used to obtain good energy resolution from detectors in which only one polarity type of carriers is efficiently collected. Experimental results using a CdZnTe detector demonstrate the effectiveness of this method. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112523
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  • 10
    Electronic Resource
    Electronic Resource
    Potential decoupling of trends in distribution area and population size of species with climate change (2005)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Global climates are changing rapidly and biological responses are becoming increasingly apparent. Here, we use empirical abundance patterns across an altitudinal gradient and predicted altitudinal range shifts to estimate change in total population size relative to distribution area in response to climate warming. Adopting this approach we predict that, for nine out of 12 species of regionally endemic birds, total population size will decline more rapidly than distribution area with increasing temperature. Two species showed comparable loss and one species exhibited a slower decline in population size with change in distribution area. Population size change relative to distribution area was greatest for those species that occurred at highest density in the middle of the gradient. The disproportional loss in population size reported here suggests that extinction risk associated with climate change can be more severe than that expected from decline in distribution area alone. Therefore, if we are to make accurate predictions of the impacts of climate change on the conservation status of individual species, it is crucial that we consider the spatial patterns of abundance within the distribution and not just the overall range of the species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2005.00995.x
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