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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 13 (1985), S. 59-64 
    ISSN: 1432-1017
    Keywords: Melittin ; fluorescence ; lifetime ; anisotropy ; tetramer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The fluorescence lifetime and rotational correlation time of the tryptophan residue in melittin, as both a monomer and tetramer, have been measured between pH 6 and 11. The fluorescence decays are non-exponential and give lifetimes of 0.7±0.1 ns and 3.1±0.1 ns. This emission is consistent with a model in which the tryptophan residue is in slightly different environments in the protein. In a dilute solution of monomer the mean fluorescence lifetime is 2.3±0.1 ns, below pH 10, but falls to 1.7 ns at higher pH. In contrast, the melittin tetramer has a mean fluorescence lifetime of only 2.2 ns at pH 6, which falls to 1.9 ns by pH 8, and falls again above pH 10 to the same value as in monomeric melittin. The behaviour between pH 6 and 8 is explained as the quenching of the Trp residue by lysine groups, which are near to the Trp in the tetramer but in the monomer, are too distant to quench. Fluorescence anisotropy decays show that the Trp residue has considerable freedom of motion and the range of “wobbling” motion is 35±10° in the tetramer
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 11 (1985), S. 243-248 
    ISSN: 1432-1017
    Keywords: Fluorescence lifetime ; tryptophan residues ; neurotoxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The fluorescence lifetime and rotational correlation time of the single tryptophan residue in α-cobratoxin have been measured between pH 2 and 10. The fluorescence decays are non-exponential and give lifetimes that are shorter than normally observed in small proteins (0.3 ns and 1 ns). This emission is consistent with a model in which the tryptophan residue is in slightly different environments in the protein. Fluorescence anisotropy decays show that the tryptophan residue is almost completely immobilised by neighbouring groups in the protein. The range of the “wobbling” motion is slightly pH dependent and limited to between 5° and 10°.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 600-603 (Sept. 2008), p. 1313-1316 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Material properties of GaN thin films grown on 3C-SiC/semiconductor-on-insulator (SOI)substrate, by metalorganic chemical vapor deposition technology, are studied by X-ray diffraction,photoluminescence and Raman scattering, with data indicating the high quality of GaN films. Ourresults have shown that SiC/SOI structures obtained by carbonization have the potential to serve asuseful substrates for GaN growth
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5921-5926 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoluminescence spectra of InAsP/InP strained multiple quantum wells have been experimentally determined in the temperature range 7–300 K. In order to understand the temperature behavior of the photoluminescence, a theoretical calculation is presented that takes into account the temperature-induced variations in band gap, carrier effective mass, biaxial strain, and exciton binding energy. The results show that the energy of the transition E1H between the n=1 electron subband and the n=1 heavy-hole subband changes as a function of temperature, and depends mainly on the evolution of the strained band gap of the InAsP layers. This is because in the temperature range 7–300 K the variations of the electron subband energy and the exciton binding energy are much less than those of the strained band gap, while the variation of the heavy-hole subband energy can be neglected. These results also explain why, for a lattice-matched quantum well, the variation of exciton peak energies with temperature follows that of the forbidden energy gap of the bulk material in the well.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2398-2405 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth and structural properties of InP, InAs/InP strained single quantum wells and short-period InAs/InP strained layer superlattices by atomic layer epitaxy. A self-limiting growth close to 1 monolayer/cycle has been obtained for InP and for InAs with low substrate temperatures between 350 and 360 °C. The samples were grown on InP (001) substrates and characterized by high resolution x-ray diffraction, grazing-incidence x-ray reflectometry, and Raman spectroscopy. The interference of x-ray wave fields in the grown structures observed by both types of x-ray measurements can be used to measure nondestructively the thickness of the deposited films with relatively high precision. High resolution x-ray diffraction and grazing-incidence x-ray reflectometry of the InAs/InP superlattices confirm the periodicity of the structures in agreement with theoretical predictions. Raman spectroscopy shows doublets of folded acoustic modes as well as InAs-like and InP-like confined longitudinal optical phonons in the InAs/InP superlattices. Results indicate that, despite the 3.2% lattice mismatch, atomic layer epitaxy is a powerful method for fabricating highly strained structures with atomically controlled heterointerfaces.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2460-2465 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of high-purity InP on various As-, S-, and Fe-doped InP substrates has been investigated using high-resolution photoluminescence spectroscopy (PL) and high-resolution x-ray diffractometry. Substrate induced strains of −7×10−5 or less have been observed using low-temperature PL. In this way information about the strain dependence of the electronic excited states of the donor bound excitons in InP was obtained. In addition, it was shown that the assessment of variations in substrate lattice parameter can be determined with a resolution of at least 5×10−6 by PL techniques.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4983-4989 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured Raman scattering and high-resolution x-ray diffraction from highly strained [(InAs)4(InP)4]N short-period superlattices grown on InP substrates by atomic layer epitaxy at 355 °C. The InAs and InP confined phonons are observed in these highly strained short-period superlattices. The energy of the InAs confined longitudinal-optical phonon (LO) modes of a fully strained superlattice (with N=8) is blue shifted by about 10 cm−1 compared to the LO phonon of bulk InAs. This effect is explained by the large biaxial strain existing in the InAs layers. The observed frequency shift agrees with the lattice-mismatch strain given by elasticity theory and independently measured by high-resolution x-ray diffraction. No evidence of a frequency shift of the InP confined LO modes in the N=8 fully strained superlattice is observed, indicating that the strain is confined to the InAs layers. We show that in a partially relaxed superlattice (with N=20), the InAs layers are in compression, while the InP layers are in tension. In this case the InP confined LO1 phonons are red shifted by about 3 cm−1 compared to the InP LO1 phonons of the N=8 fully strained superlattice, and the shift of the InAs confined LO phonons with respect to the LO phonons of bulk InAs is also reduced.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1119-1121 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Inductively coupled plasma (ICP) etch rates for GaN are reported as a function of plasma pressure, plasma chemistry, rf power, and ICP power. Using a Cl2/H2/Ar plasma chemistry, GaN etch rates as high as 6875 A(ring)/min are reported. The GaN surface morphology remains smooth over a wide range of plasma conditions as quantified using atomic force microscopy. Several etch conditions yield highly anisotropic profiles with smooth sidewalls. These results have direct application to the fabrication of group-III nitride etched laser facets. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 882-884 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report transport measurements on a series of high purity InAs epilayers grown on GaAs substrates by metalorganic chemical vapor deposition using tertiarybutylarsine and trimethylindium. Perfectly specular surfaces were obtained by a two step growth method consisting of a 400 °C prelayer followed by deposition of the thick bulk layer at higher growth temperatures. Temperature dependent Hall measurements between 1.8 and 293 K showed a competition between bulk and surface conduction, with average Hall mobilities of up to 1.2×105 cm2/V s at 50 K. Large changes in the temperature dependent transport data are observed several hours after Hall contact formation and appear to be due to passivation of the surface accumulation layer by native oxide formation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1576-1578 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single monolayers of InAs in GaAs and GaAs in InAs have been grown by atomic layer epitaxy (ALE) at 50 Torr. In situ reflectance difference spectroscopy monitoring of the surface during each stage of the growth showed a strong asymmetry in the surface behavior between the two systems. Following insertion of an InAs monolayer in GaAs, approximately 20 ML of GaAs are required to recover an In-free, As-stabilized GaAs surface at 390 °C. On the other hand, following the insertion of 1 ML of GaAs in InAs, the spectrum returns to a Ga-free, As-stabilized InAs surface after only 1 ML of InAs deposition. This behavior shows clear evidence of the presence of segregation caused by thermodynamic factors even at the very low growth temperatures used for ALE. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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