Browsing by Subject "Thallium compounds"

Now showing 1 - 6 of 6

Open Access
Dependence of the photoluminescence of Tl2InGaS4 layered crystal on temperature and excitation intensity
(Pergamon Press, 1998) Gasanly, N. M.; Serpengüzel, A.; Gürlü, O.; Aydınlı, A.; Yılmaz, I.
The emission band spectra of Tl2InGaS4 layered crystals were investigated in the 10-120 K temperature range and in the 540-860 nm wavelength range using photoluminescence (PL). The peak energy position of the emission band is located at 1.754 eV (707 nm) at 10 K. The emission band has a half-width of 0.28 eV and an asymmetric Gaussian lineshape. The increase of the half-width of the emission band, the blue shift of the emission band peak energy and the quenching of the PL with increasing temperature is explained using the configuration coordinate model. The blue shift of the emission band peak energy and the sublinear increase of the emission band intensity with increasing excitation intensity is explained using the inhomogenously spaced donor-acceptor pair recombination model. © 1998 Elsevier Science Ltd. All rights reserved.
Open Access
Low-temperature phase transitions in TlGaS2 layer crystals
(Pergamon Press, 1993) Aydınlı, Atilla; Ellialtioǧlu, R.; Allakhverdiev, K. R.; Ellialtioǧlu, S.; Gasanly, N. M.
Polarized Raman scattering spectra of TlGaS2 layer crystals have been studied for the first time as a function of temperature between 8.5 and 295 K. No evidence for a soft mode behaviour has been found. The anomalies observed in the temperature dependence of low- and high-frequency phonon modes at ∼ 250 and ∼ 180 K, respectively, are explained as due to the phase transitions. It is supposed that the phase transitions are caused by the deformation of structural complexes GaS4, rather than by slippage of Tl atom channels in [110] and [110] directions, which is mainly responsible for the appearance of the low-temperature ferroelectric phase transitions in other representatives of TlBX2 layer compounds. © 1993.
Open Access
Low-temperature photoluminescence spectra of TlInxGa1-xS2 layer mixed crystals
(Pergamon Press, 1995) Allakhverdiev, K. R.; Gasanly, N. M.; Aydınlı, Atilla
Low-temperature photoluminescence spectra of TlInS2, TlIn0.95Ga0.05S2 and TlIn0.8Ga0.2S2 layer crystals were studied in the temperature range 14-220 K. The temperature dependencies of bands 2.374 eV (A), 2.570 eV (E) and 2.576 eV (F) for TlInS2 are interpreted by supposing that the crystal undergoes structural phase transitions. Band A is considered to come from a donor-acceptor recombination channel. © 1995.
Open Access
Low-temperature visible photoluminescence spectra of TlGaSe2 layered crystal
(Elsevier Science Publishers B.V., Amsterdam, Netherlands, 2000) Gasanly, N. M.; Serpengüzel, A.; Aydınlı, A.; Baten, S. M. A.
The photoluminescence (PL) spectra of TlGaSe2 layered single crystals were investigated in the 8.5-35 K temperature. 0.2-15.2 W cm-2 excitation laser intensity, and in the 600-700 nm wavelength range. The PL spectrum has a slightly asymmetric Gaussian lineshape with a peak position located at 1.937 eV (640 nm) at 8.5 K. The PL is quenched with increasing temperature. The blue shift of the PL peak and the sublinear increase of the PL intensity with increasing laser intensity is explained using the inhomogenously spaced donor-acceptor pair recombination model. Analysis of the data indicates that the PL band is due to donor-acceptor recombination. A shallow acceptor level and a moderately deep donor level are, respectively, introduced at 0.012 eV above the top of the valence band and at 0.317 eV below the bottom of the conduction band. An energy-level diagram for radiative donor-acceptor pair recombination in TlGaSe2 layered single crystals is proposed.
Open Access
Radiative donor-acceptor pair recombination in TlInS2 single crystals
(Institute of Physics Publishing, 1999) Aydınlı, A.; Gasanly, N. M.; Yılmaz, I.; Serpengüzel, A.
Photoluminescence (PL) spectra of TlInS2 layered single crystals were investigated in the 500-860 nm wavelength region and in the 11.5-100 K temperature range. We observed two PL bands centred at 515 nm (2.41 eV, A band) and 816 nm (1.52 eV, B band) at T = 11.5 K and an excitation intensity of 7.24 W cm-2. A detailed study of the A band was carried out as a function of temperature and excitation laser intensity. A red shift of the A band position was observed for both increasing temperature and decreasing excitation laser intensity in the range from 0.12 to 7.24 W cm-2. Analysis of the data indicates that the A band is due to radiative transitions from the moderately deep donor level located at 0.25 eV below the bottom of the conduction band to the shallow acceptor level located at 0.02 eV above the top of the valence band. An energy-level diagram for radiative donor-acceptor pair transitions in TlInS2 layered single crystals is proposed.
Open Access
Temperature-and excitation intensity-dependent photoluminescence in TlInSeS single crystals
(American Institute of Physics, 2002) Gasanly, N. M.; Aydınlı, Atilla; Yuksek, N. S.
Photoluminescence (PL) spectra of TlInSeS layered single crystals were investigated in the wavelength region 460-800 nm and in the temperature range 10-65 K. We observed one wide PL band centred at 584 nm (2.122 eV) at T = 10 K and an excitation intensity of 7.5 W cm-2. We have also studied the variation of the PL intensity versus excitation laser intensity in the range from 0.023 to 7.5 W cm-2. The red shift of this band with increasing temperature and blue shift with increasing laser excitation intensity was observed. The PL was found to be due to radiative transitions from the moderately deep donor level located at 0.243 eV below the bottom of the conduction band to the shallow acceptor level at 0.023 eV located above the top of the valence band. The proposed energy-level diagram permits us to interpret the recombination processes in TlInSeS layered single crystals.