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  • 1
    Electronic Resource
    Electronic Resource
    GaAs surface reconstruction obtained using a dry process (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2035-2037 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report attaining Ga-terminated (4×2) surface reconstruction on virgin GaAs substrates using a completely dry process at temperatures below the oxide sublimation temperature and without group V overpressure. The native oxides are removed with an electron cyclotron resonance hydrogen plasma treatment, followed by annealing at 500 °C in ultrahigh vacuum, which yields a reconstructed surface suitable for epitaxial overgrowth. Characterization by secondary ion mass spectroscopy and transmission electron microscopy reveals the complete removal of O, reduced C, and high structural order at the epilayer/substrate interface when this preparation method is used before molecular beam epitaxy. Annealing the substrate at a lower temperature yields a nonreconstructed surface possessing significant impurity concentrations, and leads to dislocation defects at the epilayer/substrate interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353148
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    An instrument for measuring circular dichroism simultaneously at all wavelengths in a limited spectral range (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1912-1915 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An instrument is described for the simultaneous measurement of circular dichroism at all wavelengths in a limited spectral range. A polychromator and a charge-coupled device (CCD), serving as multichannel sensor, are arranged behind the sample cell, which is located close to the entrance slit, in contrast to the arrangement of a monochromator before the cell and using a photomultiplier as radiation detector, as usual until now. The CCD with low-noise electronics is driven by the system clock of a microprocessing unit controlled by a quartz oscillator and works fully synchronously with modulation and acquisition cycles. This leads to a high suppression of noise and systematic deviations. An electro-optic modulator with approximately rectangular excitation voltage is used. Partial CD spectra over the range of 80 nm each down to 200 nm have been recorded. The detection of a smaller amount of substance is possible than with other modern commercial instruments such as a JASCO J-600, with the same signal-to-noise ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142391
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of trace level ions by ion chromatography with concentrator columns (1979)
    s.l. : American Chemical Society
    Analytical chemistry 51 (1979), S. 1532-1535 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac50045a040
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature characteristics of (InAs)1/(GaAs)4 short-period superlattices quantum well laser (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2018-2020 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature characteristics of (InAs)1/(GaAs)4 superlattice quantum well lasers are analyzed both experimentally and theoretically. The measured threshold current density as a function of temperature is characterized by a T0=135 K for 115 K〈T〈380 K and by T0=47 K for 420 K〈T〈480 K. The radiative and nonradiative recombination rates and the gain versus carrier density relationship in monolayer superlattice structures are calculated. Inclusion of the nonradiative recombination process is necessary to explain the observed high-temperature characteristics of these lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109521
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogen plasma removal of AlGaAs oxides before molecular beam epitaxy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 735-737 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a method for the removal of AlxGa1−xAs native oxides for 0≤x≤1, prior to molecular beam epitaxial overgrowth. The oxides formed on epilayers of AlGaAs after atmospheric exposure are removed in an electron cyclotron resonance hydrogen plasma with a substrate temperature less than 400 °C. Reflection high energy electron diffraction indicates the plasma-prepared AlGaAs surface are oxide-free and crystalline; after a vacuum anneal to 250–500 °C, GaAs or AlGaAs are epitaxially overgrown on these surfaces. Secondary ion mass spectroscopy detects C, O, and Si impurities at the interfaces, where their concentrations increase with increasing Al content of the exposed surface. The quality of the interface and the overgrown film, as observed by transmission electron microscopy, are found to be better for lower interface impurity densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108854
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  • 6
    Electronic Resource
    Electronic Resource
    (InAs)1/(GaAs)4 superlattices quantum-well laser (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 924-925 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the fabrication and performance characteristics of (InAs1)/(GaAs)4 short-period superlattice (SPS) strained quantum-well lasers emitting near 1 μm. The SPS consists of 6 periods of 1 and 4 ML of InAs and GaAs, respectively. The 250-μm-long ridge waveguide lasers have a threshold current of 10 mA, an external differential quantum efficiency of 0.35 mW/mA facet, and have operated to a temperature of 200 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106462
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxial regrowth on in situ plasma-etched AlAs/AlGaAs heterostructures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1738-1740 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial regrowth by solid-source molecular beam epitaxy (MBE) on dry etched heterostructures possessing exposed AlAs surfaces is accomplished for the first time using a vacuum integrated processing. Samples composed of multilayers of AlAs and AlGaAs are patterned with a SiO2 mask and are anisotropically etched using a low damage electron cyclotron resonance (ECR) SiCl4 plasma process. Etched samples are transferred in ultrahigh vacuum between the ECR and MBE chambers to avoid atmospheric exposure before regrowth. Microstructural analysis of the overgrown layers by scanning and transmission electron microscopy indicates that epitaxial regrowth on both the etched field and vertical sidewalls is achieved. The regrown material is found to contain microtwin plates, but few dislocations, indicating the good quality of the overgrowth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107202
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Removal of GaAs surface contaminants using H2 electron cyclotron resonance plasma treatment followed by Cl2 chemical etching (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2658-2660 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a novel dry process to remove the surface contaminants C, Si, and O from GaAs substrates. This method utilizes an electron cyclotron resonance hydrogen plasma to remove the native oxides, followed by a very brief Cl2 chemical etching of GaAs to further reduce C and Si residues, and a final vacuum anneal. Characterization by secondary ion-mass spectrometry (SIMS) typically reveals the removal of C, Si, and O at the overgrown/processed interface to the levels below the SIMS detection limit. The as-processed GaAs surface, a Ga-stabilized reconstructed (4×6), is atomically smooth, and is as clean as a surface of freshly grown GaAs epilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109277
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    The acute effects of intravenous isosorbide dinitrate during cardiac surgery (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 42 (1987), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The acute effects of intravenous isosorbide dinitrate during open heart surgery were studied in 15 adult patients. Consistent and significant (p 〈 0.001) reductions in pulmonary vascular resistance (25% before. 23% after, cardiopulmonary bypass) and mean pulmonary artery pressure (14% before, 13% after, cardiopulmonary bypass) were observed in the absence of significant changes in cardiac index, mean systemic arterial pressures or right or left atrial filling pressures. These findings indicate that after cardiopulmonary bypass, when right ventricular dysfunction with raised pulmonary vascular resistance may occur, selective reduction of right ventricular afterload with isosorbide dinitrate may prove beneficial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.1987.tb04041.x
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  • 10
    Electronic Resource
    Electronic Resource
    Diurnal changes in dissolved organic and inorganic carbon and nitrogen in a hardwater stream (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 3 (1973), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Organic and inorganic carbon and nitrogen parameters were sampled simultaneously at 6 h intervals over a diurnal period at seven stations in a small hardwater stream in southern Michigan. Concentrations and budget values (kg/day) varied up to 10-fold at individual stations and between stations. The most constant parameters were total dissolved organic carbon and nitrogen. The most variable parameter was particulate organic carbon.Significant changes were noted in all parameters as the stream passed through different stream-side habitats. Budget values facilitated interpretation of these changes over time between stations. High variability in the concentration values was introduced by large allochthonous inputs of dissolved organic matter (DOM) and water alternately adding to or diluting parameters. Distance from upstream terrestrial DOM sources, DOM residence time, the pulsed nature of DOM inputs and biological utilization of DOM have important effects on the quality and quantity of DOM that enters recipient lakes and rivers. The importance of ground-water flux and DOM content is stressed. The DOM input and turnover within hardwater streams appears t o be in rapid, dynamic equilibrium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1973.tb00060.x
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