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Article Citation - WoS: 5Citation - Scopus: 5Optical Properties of Tlgaxin1-x< Mixed Crystals (0.5 ≤ x ≤ 1) by Spectroscopic Ellipsometry, Transmission, and Reflection(Taylor & Francis Ltd, 2014) Isik, M.; Delice, S.; Gasanly, N. M.The layered semiconducting TlGaxIn1-xSe2-mixed crystals (0.5 <= x <= 1) were studied for the first time by spectroscopic ellipsometry measurements in the 1.2-6.2 eV spectral range at room temperature. The spectral dependence of the components of the complex dielectric function, refractive index, and extinction coefficient were revealed using an optical model. The interband transition energies in the studied samples were found from the analysis of the second-energy derivative spectra of the complex dielectric function. The effect of the isomorphic cation substitution (indium for gallium) on critical point energies in TlGaxIn1-xSe2 crystals was established. Moreover, the absorption edge of TlGaxIn1-xSe2 crystals have been studied through the transmission and reflection measurements in the wavelength range of 500-1100 nm. The analysis of absorption data revealed the presence of both optical indirect and direct transitions. It was found that the energy band gaps decrease with the increase of indium content in the studied crystals.Article Citation - WoS: 1Citation - Scopus: 1Pseudodielectric Dispersion in As2se3< Thin Films(Wiley-v C H verlag Gmbh, 2020) Kayed, Tarek S.; Kayed, Tarek Said; Qasrawi, Atef F.; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringHerein, X-ray diffraction, energy dispersive X-ray spectroscopy, and spectral ellipsometry techniques are used to investigate the structural, pseudo-optical, and pseudodielectric properties of arsenic selenide thin films. The stoichiometric films which are prepared by the thermal evaporation technique are found to prefer the amorphous nature of growth. While the pseudoabsorption coefficient spectra display strong absorption bands at 1.84, 1.81, 1.41, and 1.13 eV, the preferred pseudo-optical transitions happen within a direct forbidden energy bandgap of 1.80 eV. In addition, the real part of the pseudodielectric spectra displays three strong resonance peaks at critical energy values of 2.33, 1.90, and 1.29 eV. Modeling of the imaginary part of the pseudodielectric constant spectra in accordance with the Drude-Lorentz approach results in the existence of six linear oscillators. The response of arsenic selenide to elliptically polarized light signals shows that the films exhibit drift mobility, free electron concentration, and plasmon frequency values in the ranges of 0.21-43.96 cm(2) V(-1)s(-1), 1.90-58.0 x 10(19) cm(-3), and 5.8-32.0 GHz, respectively. The optical conductivity parameters for As2Se3 film nominate it as a promising candidate for the fabrication of tunneling diodes suitable for microwaves filtering up to 32.0 GHz and as thin-film transistors.
