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  • 1
    Electronic Resource
    Electronic Resource
    Intersubband transitions in partially interdiffused GaAs/AlGaAs multiple quantum-well structures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2195-2199 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Continuous tuning over the entire 8–12 μm wavelength range is demonstrated for the intersubband absorption resonance in n-doped GaAs/AlxGa1−xAs multiple quantum-well structures following partial interdiffusion of the well and barrier layers via rapid thermal annealing. The data indicate that redshifting of the intersubband absorption resonance arises both from interdiffusion-induced modification of the confining potential and from a decrease in the depolarization shift. The latter effect is due in part to a decrease in the free-carrier concentration within the Si-doped quantum wells following rapid thermal annealing. Significant diffusion of the localized Si dopant is also observed over the range of annealing temperatures investigated here. Calculated values of the Al-Ga interdiffusion coefficient, as a function of anneal temperature, indicate that Si diffusion through the heterointerfaces contributes substantially to layer intermixing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350334
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative assessment of Be acceptors in GaAs by local vibrational mode spectroscopy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 971-974 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Be-doped epitaxial layers of GaAs grown by molecular beam epitaxy have been studied by local vibrational mode spectroscopy combining infrared absorption and Raman scattering. Calibration factors for both experimental techniques have been derived which enable quantitative assessments to be made of the concentrations of Be acceptors in GaAs. In Raman spectroscopy the detection limit is ≈ 3×1018 cm−3 for as-grown layers only 10 nm in thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347289
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  • 3
    Electronic Resource
    Electronic Resource
    Redistribution of epitaxial Si on (001) GaAs during overgrowth by GaAs (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2730-2732 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We examine the stability of pseudomorphic submonolayer Si films embedded in (001) GaAs by molecular-beam epitaxy. Secondary ion-mass spectrometry depth profiling reveals the presence of 1019 Si-atoms/cm3 in the first 40 nm of the GaAs cap layer. The systematic investigation of samples having different cap thickness by Hall effect measurements and local vibrational mode Raman spectroscopy allows us to identify the site distribution of Si atoms in the cap layer and yields insight into the migration mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105898
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of low energy laser on the growth and regeneration of capillaries (1990)
    Springer
    Lasers in medical science 5 (1990), S. 381-386 
    Details
    ISSN: 1435-604X
    Keywords: HeNe laser irradiation ; Biostimulation ; Wound healing ; Capillary regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Laser light of low energy is discussed to have an accelerating effect on wound healing. The aim of the present study was to proof whether HeNe laser irradiations have a positive effect on regeneration of capillaries. For this purpose aluminium chambers were implanted in the dorsal skin flap of Syrian hamsters. After coagulation of blood vessels by means of an argon laser the tissue was irradiated daily with the low energy light of a HeNe laser. Regeneration of capillaries was studied by means of intravital microscopy. The results of the study revealed a positive effect of low dose HeNe laser irradiation on the regeneration of capillaries at day 5 after the coagulation. The measurable part of the capillaries was about 27% higher for the irradiated animals compared to controls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02032595
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  • 5
    Electronic Resource
    Electronic Resource
    Electric field effects on persistent spectral holes: Perylene in the polar polymer polyvinylbutyral (1990)
    Springer
    Applied physics 51 (1990), S. 336-341 
    Details
    ISSN: 1432-0649
    Keywords: 78.50.−w ; 61.40.−a
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigated the effects of an electric field on a spectral hole burned in the inhomogeneously broadened S 0–S 1 transition of perylene in different samples of the polar polymer polyvinylbutyral (PVB) and in cellulose nitrate. The spectral hole is broadened and reduced in depth by the electric field. It was checked experimentally for perylene in PVB that the hole area remains constant when an electric field is applied. We determined the effective matrix-induced electric dipole moment differences δμ* for perylene in different PVB samples and in cellulose nitrate. Within experimental accuracy the value of δμ* is approximately independent of the composition of PVB and its water content. For perylene in cellulose nitrate the value of δμ* is larger by a factor of 1.5 than in PVB. The results are discussed on the basis of a simple model for the electric field effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348970
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of conducting GaAs multilayers by infrared spectroscopy at oblique incidence (1990)
    Springer
    Applied physics 50 (1990), S. 7-12 
    Details
    ISSN: 1432-0630
    Keywords: 78.20 ; 78.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The electrical and geometric properties of GaAs multilayer structures are measured nondestructively by infrared reflectance spectroscopy (50–5000 cm−1). Using oblique incidence and both s- and p-polarizations of the probing beam, carrier concentration and thickness of the epitactic films as well as the carrier concentration of the GaAs substrate are determined. The main structures in the spectra are due to phonon reststrahlen bands, Fabry-Perot interferences and the zeros of the dielectric function leading to dips in the reflectance (Berreman Mode). The results compare favorably with a depth-resolved secondary ion mass spectrometric (SIMS) sample analysis. The range of applicability of the method is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323946
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  • 7
    Electronic Resource
    Electronic Resource
    1H NMR and molecular mechanics studies of epimeric ethyl esters of 20(R, S)-hydroxy-23-norcholanoic acids (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 137-142 
    Details
    ISSN: 0749-1581
    Keywords: 20(R,S)-Hydroxy-23-norcholanoic acid derivatives ; 1H NMR ; Pyridine-induced shifts ; Molecular mechanics calculations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton chemical shifts for the C-18, C-21, —CO2CH2CH3 and —CO2CH2CH3 protons of epimeric ethyl esters of 20(R,S)-hydroxy-23-norcholanoic acids were measured in deuteriochloroform and pyridine-d5. The observed solvent shifts due to specific OH - pyridine hydrogen-bonded complexes allowed the quantification of the epimeric mixtures by analysis of the pyridine-d5 1H NMR spectra. The main features of the pyridine-induced shifts are rationalized in terms of the preferred conformations for the 20R- and 20S-epimers, which are predicted by molecular mechanics calculations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290208
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