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Article Citation - WoS: 24Citation - Scopus: 22Spectroscopic Ellipsometry Study of Above-Band Gap Optical Constants of Layered Structured Tlgase2, Tlgas2 and Tlins2 Single Crystals(Elsevier Science Bv, 2012) Isik, M.; Gasanly, N. M.; Turan, R.Spectroscopic ellipsometry measurements on TlGaSe2, TlGaS2 and TlInS2 layered crystals were carried out on the layer-plane (0 0 1) surfaces, which are perpendicular to the optic axis c*, in the 1.2- 6.2 eV spectral range at room temperature. The real and imaginary parts of the pseudodielectric function as well as pseudorefractive index and pseudoextinction coefficient were found as a result of analysis of ellipsometric data. The structures of critical points in the above-band gap energy range have been characterized from the second derivative spectra of the pseudodielectric function. The analysis revealed four, five and three interband transition structures with critical point energies 2.75, 3.13, 3.72 and 4.45 eV (TlGaSe2), 3.03, 3.24, 3.53, 4.20 and 4.83eV (TlGaS2), and 3.50, 3.85 and 4.50 eV (TlInS2). For TlGaSe2 crystals, the determined critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure. (c) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 12Citation - Scopus: 12Interband Transitions in Gallium Sulfide Layered Single Crystals by Ellipsometry Measurements(Elsevier, 2013) Isik, M.; Gasanly, N. M.; Turan, R.Spectroscopic ellipsometry measurements on the GaS single crystals are presented in the energy range of 1.2 - 6.2 eV at room temperature. Optical constants; pseudorefractive index, pseudoextinction coefficient, real and imaginary parts of the pseudodielectric function were determined. Analysis of the second derivative of real and imaginary parts of the pseudodielectric constant revealed five transitions with critical point energies of 3.95, 4.22, 4.51, 4.75 and 5.50 eV. These energies were assigned to interband transitions according to theoretical study of GaS band structure available in literature. (C) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Optical constants and interband transitions of anisotropic layered structured Tl2GaInS4 crystals by spectroscopic ellipsometry(Elsevier Science Sa, 2013) Isik, M.; Gasanly, N. M.; Turan, R.Spectroscopic ellipsometry measurements were carried out on Tl2GaInS4 layered crystals for orientations of electric field vector, parallel (E//c*) and perpendicular (E perpendicular to c*) to optical axis c*. The measurements were performed in the 1.2-6.2 eV spectral range at room temperature. The real and imaginary components of the pseudodielectric function, pseudorefractive index and pseudoextinction coefficient were calculated from the analysis of ellipsometric data. The energies of interband transitions (critical points) have been found from the least-square fitting of the second derivative spectra of the pseudodielectric function. The results indicated five each interband transition structures for E//c* and E perpendicular to c* configurations. The obtained critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure given in literature. (C) 2012 Elsevier B.V. All rights reserved.
