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  • 1
    Electronic Resource
    Electronic Resource
    Effect of pressure on Raman modes in MBa"2Cu"3O"7-type materials
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 153-155 (1988), S. 264-265 
    Details
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-4534(88)90584-9
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  • 2
    Electronic Resource
    Electronic Resource
    Gas chromatographic-mass spectrometric determination of ibuprofen enantiomers in human plasma using R(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol as derivatizing reagent
    Amsterdam : Elsevier
    Journal of Chromatography B: Biomedical Sciences and Applications 656 (1994), S. 441-446 
    Details
    ISSN: 0378-4347
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0378-4347(94)80107-X
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of guest–host interactions on the guest molecule in intercalated alumino-silicate compounds (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3346-3350 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have intercalated Cr(en)3+3 and Co(en)3+3 molecules (en=ethylenediamine), in known solid-solution fractional quantities, into the highly purified layered alumino-silicate fluorohectorite. Both molecules have like chemistry, but different physical sizes as they function to prop open the interlamellar gallery. As the fractional component x in [Co(en)3+3]x[Cr(en)3+3] 1−x–fluorohectorite is systematically varied, we observe the effect of intercalation on the host crystal basal spacing and the effects of intercalation on the guest molecules. Typical of the intercalation of rigid-layer compounds with agents differing in size, the basal spacing shows a sigmoidal dependence on fractional concentration. This is due to the large, but not infinite rigidity of the host and guest constituents. The lifetime of the fluorescence emission from the Cr(en)3+3 molecule exhibits the same sigmoidal dependence, indicating that the uniaxial stress exerted on the molecule, as it props open the gallery, is the primary factor dictating the guest fluorescence properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466426
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  • 4
    Electronic Resource
    Electronic Resource
    Raman studies of nitrogen incorporation in GaAs1−xNx (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1409-1411 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report direct-backscattering Raman studies of GaAs1−xNx alloys, for x≤0.03, grown on (001) GaAs. The Raman spectra exhibit a two-mode behavior. The allowed GaAs-like longitudinal-optic phonon near 292 cm−1 is found to red shift at a rate of −136±10 cm−1/x. This is well described by the combined effects of strain and alloying. The GaN-like phonon near 470 cm−1 is observed to increase in intensity in direct proportion to x, and to systematically blue shift at a rate of 197±10 cm−1/x. This blue shift is likewise attributed to strain and alloying. The GaAs-like second-order features are also seen to broaden slightly and diminish in intensity with increasing nitrogen concentration. These results are attributed to a weak breakdown in the zincblende-crystal long-range order, possibly related to the presence of ordered domains within the random alloy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121959
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  • 5
    Electronic Resource
    Electronic Resource
    Visible and ultraviolet Raman scattering studies of Si1−xGex alloys (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2523-2528 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report Raman studies of the Si–Si phonon band in Si1−xGex alloys, where the excitation is by visible and ultraviolet (351 nm) light. At a wavelength 351 nm, the optical penetration depth is extremely shallow ((approximate)5 nm). By varying the excitation from 351 to 514 nm, the optical penetration depth spans from 5 to 300 nm. Two sets of samples were examined. Thin layers grown using molecular beam epitaxy were coherently strained to match the lattice constant of the silicon substrate. Thick layers grown using organo–metallic chemical vapor deposition were strain relaxed. For the thin, strained layers, visible excitation produces a spectrum, which is a superposition of the substrate and the epilayer phonon bands. Reducing the wavelength (and, consequently, penetration depth) allows us to isolate the epilayer spectrum. Phonon energies obtained using all excitation wavelengths agree. We conclude that Raman scattering from these alloys using 351 nm laser light gives us bulk alloy properties pertinent to the near-surface composition and strain. The epilayers show no evidence of compositional variance or strain relaxation near the surface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287757
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  • 6
    Electronic Resource
    Electronic Resource
    Composition dependence of the optical phonon energies in hexagonal AlxGa1−xN (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7977-7982 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report optical studies on AlxGa1−xN alloy layers across the full composition range. The series of alloy layers was grown on (111)-oriented silicon substrates using gas-source molecular beam epitaxy. From reflectance measurements, we determine the composition dependence of the energy gap to be Eg=3.42+1.18x+1.56x2, in good agreement with previous work. By combining Fourier transform infrared and Raman spectroscopy studies, we determine the composition dependence of phonons having A1(TO), E1(TO), E22, A1(LO), and E1(LO) symmetry. The longitudinal optic phonons exhibit one-mode alloy behavior. Two-mode alloy behavior is observed for all transverse optic and the E22 phonons (i.e., each mode has AlN-like and GaN-like branches). All phonons are seen to blueshift with increasing x. The influence of stress on the phonon energies is discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1372661
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  • 7
    Electronic Resource
    Electronic Resource
    Raman studies of heavily carbon doped GaAs (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7224-7230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectroscopy is used to study GaAs heavily doped with carbon. Hole concentrations in these samples range from 2.3×1019 to 1×1020 cm−3. Three main Raman features are investigated: the longitudinal-optic (LO) phonon mode, the substitutional carbon-at-arsenic local-vibrational mode, and the coupled plasmon–LO phonon present due to the interaction between the LO phonon and the free carriers. Only one allowed phonon-like coupled mode is observed due to the large plasmon damping and high effective carrier masses. The coupled mode is seen to systematically redshift as carrier concentration increases. This behavior is described by a model which includes the effects of high hole concentrations on the dielectric function and an additional shift in the optic phonon we tentatively attribute to carbon size effect. The local vibrational mode intensity is found to be directly proportional to the carrier concentration p. Interestingly, the local mode intensity shows good correlation with that of the coupled plasmon–LO phonon mode as a function of p. The ratio of the coupled plasmon–LO phonon mode intensity to that of the LO phonon is found to be directly proportional to the carrier concentration. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370536
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  • 8
    Electronic Resource
    Electronic Resource
    Raman-scattering studies of silicon-implanted gallium arsenide: The role of amorphicity (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 1946-1951 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of Raman-scattering experiments were carried out on GaAs implanted with Si+ and with SiF+3 ions, both before and after annealing, for samples subjected to fluences spanning a wide range. The implantation-induced amorphization of the damage layer was cleanly observed via the evolution, with increasing fluence, of the broad three-band continuum of amorphous GaAs which extends from near zero up to 300 cm−1. Annealing recovers the simple line spectrum of crystalline GaAs, but with a changed longitudinal-optical/transverse-optical intensity ratio which indicates a departure from epitaxial regrowth. Three lines observed near 400 cm−1 in heavily implanted samples were identified with silicon vibrational local modes. The effect of annealing on these local-mode lines is not an intensity increase but is instead a line narrowing which reveals an annealing-induced sharpening of the distribution of local settings sampled by the substitutional silicons. In particular, a line (at 381 cm−1) assigned to the Si-at-a-Ga-site donor impurity is clearly seen before annealing, even though annealing is needed to transform the highly resistive implanted material into semiconducting n-type GaAs. We propose that the primary role of annealing in the "electrical activation'' of implanted semiconductors is not to shift the impurity atoms into substitutional donor or acceptor sites (they already occupy such sites), but is instead to recover the high carrier mobility of the crystalline form. "Healing'' and "activation'' thus correspond to the same process, the elimination of amorphicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336423
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  • 9
    Electronic Resource
    Electronic Resource
    Ultraviolet Raman stress mapping in silicon (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2008-2010 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report micro-Raman stress imaging in silicon structures using 351 nm excitation. This excitation has an extremely shallow optical penetration depth ((approximate)5 nm) in silicon. It should also ultimately provide higher spatial resolution compared to visible wavelengths used in micro-Raman studies. As a test we examine a wafer which consists of a patterned nitride/polycrystalline silicon/oxide/substrate "stack" with neighboring regions of device-quality silicon covered only by a thin oxide layer. We obtain two-dimensional images with spatial resolutions ranging from 1 to 4 μm. The smallest Raman shift reliably detectable is found to be ±0.07 cm−1, corresponding to a stress magnitude of 35 MPa. Stresses on the order of 140 MPa are observed beneath the stack region. The contrasting linewidths between the substrate and polycrystalline silicon provide a complementary image. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123729
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  • 10
    Electronic Resource
    Electronic Resource
    Micro-Raman imaging of GaN hexagonal island structures (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1757-1759 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use Raman scattering to obtain a stress map of lateral epitaxy overgrown GaN. Isolated hexagonal islands are grown by selective area overgrowth without a seed layer. Stress mapping is obtained from shifts in the E2 phonon. GaN in the aperture area has the greatest biaxial compressive stress, (approximate)0.18 GPa. The overgrowth region is under slightly smaller stress, about 0.15 GPa. We attribute marked variations in the A1(LO) phonon intensity to spatial variations in the free carrier concentration. This is found to be small in the aperture region and high in the lateral overgrowth. The position-dependent presence of the lower coupled plasmon–phonon band is consistent with this interpretation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124810
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