Browsing by Subject "Raman-scattering"

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    Coupled plasmon-LO-phonon modes in GaInAs quantum wires
    (American Institute of Physics., 1996-06-20) Mutluay, N.; Tanatar, Bilal
    We study the collective excitation modes of coupled quasi-one-dimensional electron gas and longitudinal-optical phonons in GaInAs quantum wires within the random-phase approximation. In contrast to the higher-dimensional systems, the plasmon-phonon coupling is found to be strong at all Linear carrier densities of interest. We calculate the oscillator strength of the numerically evaluated coupled modes and the Raman scattering intensity. The effect of phenomenological LO-phonon broadening on the collective excitation spectrum is also investigated. (C) 1996 American Institute of Physics.
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    Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence
    (AIP Publishing, 2006) Yerli, S.; Serincan, U.; Dogan, I.; Tokay, S.; Genisel, M.; Aydınlı, Atilla; Turan, R.
    Silicon nanocrystals, average sizes ranging between 3 and 7 nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800 degrees C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.
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    Free-standing ZnO-CuO composite nanowire array films and their gas sensing properties
    (IOP Publishing, 2011-07-19) Wang, J. X.; Sun, X. W.; Yang, Y.; Kyaw, A. K. K.; Huang, X. Y.; Yin, J. Z.; Wei, J.; Demir, Hilmi Volkan
    A modified hydrothermal method was developed to synthesize ZnO-CuO composite nanostructures. A free-standing film made of ZnO-CuO nanostructures was assembled on the surface of the hydrothermal solution with a smooth surface on one side and a spherical surface on the other side. The structure, growth mechanism and the optical properties of the composite nanostructures were studied. Structural characterizations indicate that the composite nanostructure mainly consisted of two single-crystal phases of CuO and ZnO. The sensitivity for CO gas detection was significantly improved for the composite CuO-ZnO nanostructure film. This method offers a possible route for the fabrication of free-standing nanostructure films of different functional composite oxides.
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    Quantum dots on vertically aligned gold nanorod monolayer: plasmon enhanced fluorescence
    (Royal Society of Chemistry, 2014) Peng, B.; Li, Z.; Mutlugun, E.; Martinez, P. L. H.; Li, D.; Zhang, Q.; Gao, Y.; Demir, Hilmi Volkan; Xiong, Q.
    CTAB-coated Au nanorods were directly self-assembled into a vertically aligned monolayer with highly uniform hot spots through a simple but robust approach. By coupling with CdSe/ZnS quantum dots, a maximum enhancement of 10.4 is achieved due to: increased excitation transition rate, radiative rate, and coupling efficiency of emission to the far field.