Synthesis and thermoelectric power measurements of TlGaSe 2 single crystals
TlGaSe2single crystals were grown by modified Bridgman method. Thermoelectric power measurement were carried out in a brass working chamber designed for this purpose, allow measurements in a wide range of temperature under vacuum. The experimental results indicates that TlGaSe2 is of p-type conductivity. Throughout these measurements, various parameters such as effective mass of charge carriers, carrier mobility, diffusion coefficient, relaxation time and diffusion length for both majority and minority carriers were found. In addition to these pronounced parameters, the efficiency of the thermoelectric element (figure of merit) was evaluated, which leads to better application in many fields. [A. T. Nagat, S. A. Hussein, S. E. Al Garni. Synthesis and thermoelectric power measurements of TlGaSe2 single crystals. Life Sci J 2014;11(8):418-422]. (ISSN:1097-8135). http://www.lifesciencesite.com. 54
Optical and photoelectric properties of TlGaSe2 layered crystals
Abstract Absorption spectra of thin layers of TlGaSe2 crystals are used to study the energy gap and the interband transitions of the compound in the energy region 1.5–3.8 eV and in the temperature range 12–290K. A peak of excitonic origin appears at 2.39 eV at 12 K, 0.3 eV above the fundamental direct gap. It is followed by two sharp structures at 2.49 eV and 2.56 eV (12K). A broad structure appears at 2.64 eV. A room temperature reflection spectrum is also presented. The temperature dependence of the critical energies of all the observed structures is given. The dependence of the broadening parameter on temperature and the binding energy of the main exciton peak are also presented. Photoconductivity measurements at 290K and 90K resolve a number of structures that can be identified with several optical transitions. A peak associated with an acceptor level at 0.43 eV above the valence band maximum is also registered.
Raman Scattering in Ferroelectric TlGaSe2. Soft Mode and Order Parameter
The Raman scattering spectra of soft and rigid modes in TlGaSe2 are investigated over a wide temperature range. The interaction between soft and rigid modes is observed from the description of the experimental spectrum within a model of interacting harmonic oscillators. Temperature dependences of the soft mode frequency and halfwidth are confirmed. The splitting of the rigid Raman mode in the ferroelectric phase is also detected. 
 
 
 
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