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  • 1
    Electronic Resource
    Electronic Resource
    Studies on the modification ofEscherichia coli ribosomal protein L7/L12 by succinic anhydride (1982)
    Springer
    Cellular and molecular life sciences 38 (1982), S. 241-243 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Lysine modification by increasing quantities of succinic anhydride in theEscherichia coli ribosomal protein L7/L12 produces loss of its ability in reconstitution of elongation-factor-G-dependent GTP hydrolysis and polyphenylalanine synthesis activities, showing lower antigenicity and loss of antigenic determinants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01945089
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  • 2
    Electronic Resource
    Electronic Resource
    Raman scattering study of (GaAs)1−x(Si2)x alloys epitaxially grown on GaAs (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4977-4980 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: (GaAs)1−x(Si2)x metastable alloys grown on (001), (110), (112), and (111) GaAs substrates, with Si fractions in the range 0≤x≤0.43, were studied by Raman scattering. Two modes near the LO and TO modes of GaAs, besides two local modes associated either with Si–As or Si–Ga and Si–Si bonds, are observed in the Raman spectra. The ratio of integrated intensities of TO-like and LO-like modes (ITO/ILO) is used to evaluate the short range order. It is observed that the zinc blende to diamond transition reported in the literature for these alloys does not influence the Si fraction dependence of the short range order. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1410886
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature dependence of the band gap of Cd1−xZnxTe alloys of low zinc concentrations (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7713-7717 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the fundamental band-gap E0 of Cd1−xZnxTe alloys with zinc concentrations in the 0 to 0.3 range has been determined by modulated photoreflectance (PR). E0 is found to vary from 1.511 eV for x=0.00 to 1.667±0.008 eV for x=0.3, at room temperature and from 1.602 eV at x=0.00 to 1.762±0.004 eV for x=0.3 at 10 K. The measured broadening parameters Γ have values between 25 and 45 meV at room temperature and decrease monotonically to values around 5 meV or smaller at 10 K. The temperature dependence of the observed band gap energies is well described by the well known Varshni formula E(T)=E(0)−AT2/(T+aitch-theta) for all samples studied. The PR temperature broadening is well understood assuming that it results from the scattering of the excitonic electron-hole pair responsible of the band-to-band transition PR signal off LO phonons. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362374
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  • 4
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of the transport process in the growth of a-Si:H prepared by cathodic reactive sputtering (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 477-482 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport process of sputtered Si atoms from the target to the substrate, crossing an argon-hydrogen plasma, is modeled by using Monte Carlo techniques. The hydrogen and argon partial pressures, the dark zone voltage, and the target-substrate distance are varied in the calculations. The effect of the above-mentioned parameters upon the thermalization and energy distribution of atoms arriving at the substrate is calculated, allowing the determination of the growth conditions that minimize the damage produced on the films by highly energetic atoms, while maintaining a reasonable growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345228
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  • 5
    Electronic Resource
    Electronic Resource
    Near band-edge optical properties of GaAs at interfaces of ZnSe/GaAs/GaAs by phase selection in photoreflectance (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 425-429 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs at the ZnSe/GaAs and GaAs/GaAs interfaces of ZnSe/GaAs/GaAs heterostructures is studied by phase selective photoreflectance (PR) spectroscopy. Four samples with ZnSe layers of various thickness were examined. We unambiguously determined the origin of two different features observed in the PR spectra by combining in phase and out of phase measurements, with PR measurements employing excitation lasers with different wavelengths. These two features are found to originate at different regions of the heterostructure. One contributing transition is a bulk-like signal, resembling that of bare GaAs, which originates in a region that encompasses the buffer layer/substrate GaAs homointerface. A second contributing signal is attributed to a strained region adjacent to the ZnSe/GaAs heterointerface. Both this second signal and the bulk-like signal show Franz–Keldysh oscillations that allow us to determine the electric field strength at the ZnSe/GaAs and GaAs/GaAs interfaces. It is found that the electric field strength at the heterointerface is larger than that of the homointerface. Reflectance difference measurements further support the existence of two spatially separated GaAs regions, which produce two independent overlapping optical modulated signals in the ZnSe/GaAs/GaAs heterostructures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370747
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  • 6
    Electronic Resource
    Electronic Resource
    Dependence on the atmosphere of preparation of the luminescence of spark processed porous GaAs (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1270-1275 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the preparation of photoluminescent porous GaAs by the application of high voltage spark discharges in atmospheres of pure oxygen, pure nitrogen, and in mixed N2:O2 ratios of 4:1 and 1:4. The spark-processed porous (spp) samples were characterized by the observation of their visible photoluminescence (PL) when illuminated with UV monochromatic radiation. Some differences are observed in the initial PL spectra of the spp-GaAs according to the atmosphere of preparation under similar sparking and time conditions. The PL consists of two dominant bands, a yellow-green band between ∼2.2 and 2.6 eV and a blue-violet band, centered at 3.1 eV. Comparison with Raman and PL results from As2O3 and As2O5 indicates that the PL in the spp-GaAs is produced by the formation of these compounds by exposure to oxygen during the preparation. This is reinforced by energy dispersive x-ray spectroscopy measurements that indicate that the spp-GaAs is always oxidized, even when prepared under a nitrogen flow. The blue-UV emission at 3.1 eV suggests that we cannot rule out confinement as a contributing mechanism for this PL. Raman spectra indicate that for samples prepared in pure nitrogen, the resulting material consists of amorphous As and GaAs, and the cubic form of As2O3, arsenolite. PL and Raman indicate that there exists an increasing degree of amorphization of the resultant material with the introduction of nitrogen in the preparation atmosphere. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372007
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  • 7
    Electronic Resource
    Electronic Resource
    Growth of strained-layer GaAs/Ge superlattices by magnetron sputtering: Optical and structural characterization (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3209-3214 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strained layer superlattices of GaAs/Ge/GaAs and Ge/GaAs/Ge have been grown by magnetron sputtering of different intercalated layer thickness. The samples exhibited good crystallographic quality, pseudomorphic growth on the substrate, as well as superlattice characteristics. Layer periodicity, concentration profile and the thicknesses of the resultant films were examined by high-resolution x-ray diffraction, secondary ion mass spectroscopy, infrared (IR) optical transmission measurements, and Raman spectroscopy. The heterostructures exhibited IR attenuation peaks in transmission between 0.5 and 1.0 eV, whose energy position was characterized as a function of the thickness of the intercalated thinner layers. The combined results of these techniques reveal that the intended GaAs layers are in fact composed of (GaAs)1−x(Ge2)x alloys with a few percent Ge content. Experimental and theoretical results have been modeled with the transmittance model, which assumes that light hits the surface normally and takes the alternating layer thicknesses as variable parameters. Both, experimental and theoretical results agree to within 3%. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347413
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of growth direction on order–disorder transition in (GaAs)1−x(Ge)2x semiconductor alloys (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2497-2499 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We provide direct evidence of the dependence of the critical concentration of IV-type atoms at the order–disorder transition in ternary metastable (III–V)–IV, zincblende–diamond semiconductor alloys on the growth direction. The excellent agreement between the experimental and model predicted critical concentrations is evidence that the atomic ordering in these alloys is ruled almost entirely by substrate geometry. In this letter, we report the observation of the critical concentration dependence on substrate orientation in (GaAs)1−x(Ge2)x metastable alloys, epitaxially grown on (001), (111), (112), and (113) oriented GaAs. A different long-range order parameter behavior with Ge concentration is obtained for each growth direction. The Ge critical concentrations observed are 0.36, 0.96, 0.59, and 0.50±0.03, for the orientations listed above, values that compare well with those obtained from a Monte Carlo simulation of the growth, 0.33, 1.0, 0.64, and 0.54, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1318722
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  • 9
    Electronic Resource
    Electronic Resource
    Refractive indices of zincblende structure β-GaN(001) in the subband-gap region (0.7–3.3 eV) (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 441-443 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Refractive indices n and absorption coefficients α of epitaxial metastable zincblende structure β-GaN(001) were determined over the subband-gap energy range between 0.8–3.1 eV from an analysis of optical transmission spectra. n was found to vary from 2.25 to 0.8 eV (1.55 μm) to 2.50 at 3.1 eV (0.4 μm) with an energy E (eV) dependence that is well described by a Sellmeir-type dispersion relationship, n2(E)=1+148/(38.3−E2). The refractive indices of β-GaN are 3%–4% smaller than previously reported values for hexagonal α-GaN. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116406
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  • 10
    Electronic Resource
    Electronic Resource
    Excitonic transitions in (GaAs)1−x(Ge2)x/GaAs multilayers grown by magnetron sputtering (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 94-96 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on excitonic transitions observed at room temperature in multilayers of (GaAs)1−x(Ge2)x/GaAs grown by magnetron sputtering. We attribute the observation of the exciton absorption at room temperature to confinement effects on the bound electron–hole pairs inside the Ge-rich layers of the (GaAs)1−x(Ge2)x alloys. From secondary ions mass spectroscopy these layers are measured to be 50, 33, and 30 nm in full width at half maximum (FWHM), for three different samples. These layers alternate with (GaAs)1−x(Ge2)x alloy layers of very low Ge concentration that can be considered of plain GaAs, ∼360 nm in thickness for two samples and 240 nm for a third one. The observed transition energies of the exciton are very close to (approximate)1 eV both at 300 and 4 K. A calculation of exciton energy-level spacing and transition probabilities provides acceptable values for the exciton transition energies observed, considering a triangular quantum well as an approximation to the Ge profile in the confinement layers. The observed excitonic FWHM remain nearly constant at all temperatures examined (300–4 K). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120655
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