Browsing by Subject "D. Optical properties"

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    Low temperature photoluminescence spectra of InS single crystals
    (Elsevier, 1997-03) Gasanly, N. M.; Aydınlı, Atilla
    Photoluminescence (PL) spectra of InS were investigated in the wavelength region 477.5–860 nm and in the temperature range 8.5–293 K. We observed three PL bands centered at 605 nm (A-band), 626 nm (B-band) and 820 nm (C-band). The A- and B-bands are due to radiative transitions from the donor level at 0.01 eV below the bottom of the conduction band to the valence band and from the donor level at 0.06 eV below the bottom of the conduction band to the acceptor level 0.12 eV above the top of the valence band, respectively. The proposed energy-level scheme allows us to interpret the recombination processes in InS single crystals. Copyright © 1997 Published by Elsevier Ltd.
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    Low-temperature photoluminescence spectra of layered semiconductor TlGaS2
    (Pergamon Press, 1998) Gasanly, N. M.; Aydınlı, Atilla; Bek, A.; Yilmaz, I.
    Photoluminescence (PL) spectra of TlGaS2 layered single crystals were studied in the wavelength region 500-860 nm and in the temperature range 9.5-293 K. We observed a total of three PL bands centered at 568 nm (2.183 eV, A-band), 718 nm (1.727 eV, B-band) and 780 nm (1.590 eV, C-band) at various temperatures. We have also studied the variations of the A- and B-band intensities vs excitation laser density in the range from 7 × 10-2 to 9 W cm-2. The A- and B-bands were found to be due to radiative transitions from the deep donor levels located at 0.362 and 0.738 eV below the bottom of the conduction band to the shallow acceptor levels at 0.005 and 0.085 eV located above the top of the valence band, respectively. The proposed energy-level diagram permits us to interpret the recombination processes in TlGaS2 layered single crystals. © 1997 Elsevier Science Ltd.
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    Temperature-dependent Raman scattering spectra of ε-GaSe layered crystal
    (Elsevier Science, 2002) Gasanly, N. M.; Aydnl, A.; Özkan, H.; Kocabaş, C.
    The temperature dependencies (15-300 K) of seven Raman-active mode frequencies and linewidths in layered gallium selenide have been measured in the frequency range from 10 to 320 cm-1. We observed softening and broadening of the optical phonon lines with increasing temperature. Comparison between the experimental data and theories of the shift and broadening of the intralayer phonon lines during heating of the crystal showed that the experimental dependencies can be explained by the contributions from thermal expansion, lattice anharmonicity and crystal disorder. The pure-temperature contribution (phonon-phonon coupling) is due to three-phonon processes. Moreover, it was established that the effect of crystal disorder on the linewidth broadening of TO mode is stronger than that of LO mode.