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  • 1
    Electronic Resource
    Electronic Resource
    Raman spectroscopic characterization of KrF-laser-irradiated silicon (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2472-2477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-fluence KrF-laser-irradiated silicon wafers exhibit a wealth of surface structures, which are different depending on the medium present above the surface during treatment with ultraviolet light. A special surface feature, appearing after treatment under water and in air, is analyzed with a Raman microprobe spectrometer. It is found to consist of leaflike formed silicon structures located above but still attached to the treated surface. During Raman scattering measurements the temperature of these morphological peculiarity rises considerably even at low cw probe laser powers because of geometrically limited thermal conductivity. It is shown that the temperatures, which were derived from the Stokes–to–anti-Stokes scattering intensity ratio are more reliable than those extracted from line shifts since the stress developing inside the Raman laser-heated leaflike microstructures is not known. A Raman microprobe scan of a damage spot, generated by UV treatment under water, reveals in the most cases an enhanced Raman intensity (factor of 10) in comparison with untreated areas. This enhancement is even larger at surface spots of smaller (≤1 μm) sizes and is attributed to the field enhancement of the incident and scattered radiation field caused by geometrical resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351593
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  • 2
    Electronic Resource
    Electronic Resource
    Far-infrared measurements of the mobility and carrier concentration in lightly doped GaAs on Si(100) (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 631-637 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs layers with thicknesses from 1 to 8 μm were grown by molecular-beam epitaxy onto Si(100) substrates. These epitaxial layers were lightly doped with Si (ND(approximately-equal-to)2×1016 cm−3). The determination of accurate numbers for the carrier concentrations and mobilities in the GaAs is complicated by the low doping and the dimensions of the films. However, a new approach in IR spectroscopy that combines a conventional reflectance measurement from 50 to 500 cm−1 with a transmittance measurement in the very far-infrared range from 12 to 62 cm−1 is demonstrated to provide precise information on both carrier concentrations and mobilities. A comparison of the results obtained at room temperature from IR and Hall measurements reveals that the nondestructive IR technique is an easy to perform and excellent characterization tool for the Ga As layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351845
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  • 3
    Electronic Resource
    Electronic Resource
    Spectroscopic observation of the b 1Σ+→X˜ 3Σ− transition of AsH (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7094-7096 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Emission lines of the b 1∑+→X˜ 3∑− transition of AsH radicals have been detected in the fluorescence of a dc-glow-discharge of arsine in hydrogen. From measurements of line positions of the (0,0), (1,1), and (2,2) Q branches and the (0,0) P and R branches, the molecular constants of the b 1∑+ state were determined: Te=14 178.0 cm−1, B0=7.2467 cm−1, D0=3.1528⋅10−4 cm−1, ωe=2213 cm−1, ωexe=47.5 cm−1, re=152.937 pm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459432
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamic study of the surfaces of (001) gallium arsenide in metal-organic vapor-phase epitaxy during arsenic desorption (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1245-1250 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated by reflectance anisotropy spectroscopy the arsenic desorption from GaAs (001) at various temperatures in metal–organic vapor-phase epitaxy to obtain reaction orders and activation energies. The highest arsenic coverage, found at low temperatures with arsine stabilization, corresponds to a (4×3) reconstruction. Without arsine, arsenic starts to desorb and less arsenic-rich reconstructions are observed, depending on temperature: c(4×4) (below 800 K), β2(2×4) (below 920 K), α(2×4), and only with hydrogen carrier gas finally (4×2) (above 950 K). Above 920 K the reaction order differs in hydrogen and nitrogen atmosphere, probably due to an etching effect of hydrogen radicals. The five different desorption processes show either a first- or zero-order time dependence. First order is related to the desorption from the terraces and zero order to desorption from the steps (or kinks) on the surfaces. The activation energies for all processes are around 2.5 eV. This energy is, therefore, assumed to be the activation energy for the removal of an arsenic dimer from the surface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372003
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  • 5
    Electronic Resource
    Electronic Resource
    Separation of Neuropeptides by HPLC: Evaluation of Different Supports, with Analytical and Preparative Applications to Human and Porcine Neurophysins, β-Lipotropin, Adrenocorticotropic Hormone, and β-Endorphin (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 44 (1985), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The separation of 38 hypophyseal or hypothalamic peptides and proteins by reversed-phase HPLC is described. The efficacy of several supports is discussed: large-pore reversed-phase silica supports turned out to be most effective in the separation of neuropeptides and proteins. The use of high sodium phosphate and phosphoric acid in the eluent resulted in high yields and better separation. On the basis of this procedure, β-lipotropin, β-endorphin, and adrenocorticotropic hormone were prepared from porcine pituitary glands, and human neurophysins from human pituitary posterior lobes. Moreover, this system is used for the analysis of the perifusate of pituitary posterior lobes, showing the release of microheterogeneous neurophysins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1985.tb07156.x
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  • 6
    Electronic Resource
    Electronic Resource
    Enzymic cyclization of 15-norsqualene 2,3-oxide (1968)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 90 (1968), S. 3284-3286 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01014a081
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular-beam-epitaxy growth of CdTe on InSb (110) monitored in situ by Raman spectroscopy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4060-4065 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: CdTe epitaxial layers were deposited on clean cleaved InSb(110) substrates by molecular-beam epitaxy at room temperature and elevated temperatures. The formation of interface and layer was investigated using Raman spectroscopy as a growth monitor, i.e., Raman spectra were taken on line without interruption of the deposition process. Fabry–Pérot interference of the incident as well as the scattered light within the heterostructure leads to a characteristic modulation of the substrate phonon scattering intensity. The modulation is calculated and serves as a measure for the layer thickness. For the deposition at elevated temperatures the true surface temperature is determined from the InSb TO phonon frequency shift. While at a substrate temperature of 150 °C the crystalline quality of the CdTe layer was improved compared to room-temperature growth, the deposition of CdTe at 300 °C resulted in the formation of a layer consisting of In2Te3 and liberated Sb. The effect of the laser radiation on the growth process at different temperatures is also discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359862
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  • 8
    Electronic Resource
    Electronic Resource
    In situ reflectance anisotropy studies of AlxGa1−xAs layers grown on GaAs(001) by molecular beam epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3115-3120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflectance anisotropy spectroscopy was used to examine the surfaces of AlxGa1−xAs layers grown on GaAs(001) by molecular beam epitaxy, where the Al mole fraction was varied across the whole composition range x=(0.0,0.25,0.50,0.75,1.0). All surfaces were also independently characterized using reflection high-energy electron diffraction, and were found to exhibit a c(4×4) reconstruction. After initial changes in the spectra were observed on depositing very thin layers (≤20 monolayers), in the intermediate thickness range a regime was entered in which strong optical interference effects appeared. These effects are accurately accounted for using a four-media model. For thicker layers (≥8000 monolayers), interference effects were seen to diminish and spectra representative of the surfaces of bulk AlxGa1−xAs were obtained. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358663
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  • 9
    Electronic Resource
    Electronic Resource
    Raman monitoring of semiconductor growth (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7330-7333 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper it is demonstrated that Raman spectroscopy can be used for in situ online monitoring of semiconductor layer growth. For this purpose an ultra-high-vacuum chamber was designed to suit molecular beam epitaxial growth as well as simultaneous optical measurements utilizing a multichannel detection Raman system. As a result Raman spectra can be taken while growth progresses. As shown by the example of InSb growth, they provide information on the interface chemistry, crystal quality of the growing layer, and the growth mode as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356644
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  • 10
    Electronic Resource
    Electronic Resource
    Assessment of clustering induced internal strain in AlInAs on InP grown by molecular beam epitaxy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2459-2465 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature photoluminescence (PL) and Raman measurements were performed on AlInAs grown lattice matched to InP by molecular beam epitaxy at reduced growth temperature (Ts). The PL of layers grown at Ts above 500 °C is dominated by excitonic emission, whereas for lower Ts donor-acceptor related transitions prevail. Below a critical Ts of 450 °C a marked shift towards lower emission energies with a maximum shift near 400 °C is observed that is attributed to a modified band edge due to clustering. Comparable trends are detected by Raman spectroscopy. The observed reduction of the separation of the InAs- and AlAs-like longitudinal optical phonon modes (LOInAs and LOAlAs) demonstrates local internal strain to be present as a result of clustering. This effect reaches a maximum for Ts at 400 °C. A shift of the LOInAs solely accounts for this behavior. In addition strong asymmetric broadening of the LOAlAs-phonon line observed on low Ts material indicates an increasing reduction of the correlation length and suggests the structural disorder to be correlated with the AlAs sublattice. Taking into account the pressure dependence of the AlInAs energy gap and the frequency shift of the LOInAs phonon, the local internal strain equivalent pressure was calculated from the PL and Raman results, respectively, giving similar values of up to 5 kbar for material grown at 400 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357597
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