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Article Citation - WoS: 1Citation - Scopus: 1Structural and Optical Properties of Thermally Evaporated Ga-In Thin Films(World Scientific Publ Co Pte Ltd, 2014) Isik, Mehmet; Gullu, Hasan HuseyinIn this paper, structural and optical properties of Ga-In-Se (GIS) thin films deposited by thermal evaporation technique have been investigated. The effect of annealing was also studied for samples annealed at temperatures between 300 degrees C and 500 degrees C. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have been used for structural characterization. It was reported that increase of annealing temperature results with better crystallization and chemical composition of the films were almost same. Optical properties of the films were studied by transmission measurements in the wavelength range of 320-1100 nm. The direct bandgap transitions with energies in the range of 1.52 eV and 1.65 eV were revealed for the investigated GIS films. Photon energy dependence of absorption coefficient showed that there exist three distinct transition regions for films annealed at 400 degrees C and 500 degrees C. The quasicubic model was applied for these transitions to calculate crystal-field splitting and spin-orbit splitting energy values.Article Citation - WoS: 32Citation - Scopus: 32Temperature Dependence of the Band Gap, Refractive Index and Single-Oscillator Parameters of Amorphous Indium Selenide Thin Films(Elsevier Science Bv, 2007) Qasrawi, A. F.InSe thin films are obtained by evaporating InSe crystal onto ultrasonically cleaned glass substrates under pressure of similar to 10(-5) Torr. The structural and compositional analysis revealed that these films are of amorphous nature and are atomically composed of similar to 51% In and similar to 49% Se. The reflectance and transmittance of the films are measured at various temperatures (300-450 K) in the incident photon energy range of 1.1-2.1 eV. The direct allowed transitions band gap - calculated at various temperatures - show a linear dependence on temperature. The absolute zero value band gap and the rate of change of the band gap with temperature are found to be (1.62 +/- 0.01) eV and -(4.27 +/- 0.02) x 10(-4) eV/K, respectively. The room temperature refractive index is estimated from the transmittance spectrum. The later analysis allowed the identification of the static refractive index, static dielectric constant, oscillator strength and oscillator energy. (c) 2006 Elsevier B.V. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 4Optical Characterization of Ga2ses Layered Crystals by Transmission, Reflection and Ellipsometry(World Scientific Publ Co Pte Ltd, 2015) Isik, Mehmet; Gasanly, NizamiOptical properties of Ga2SeS crystals grown by Bridgman method were investigated by transmission, reflection and ellipsometry measurements. Analysis of the transmission and reflection measurements performed in the wavelength range of 400-1100 nm at room temperature indicated the presence of indirect and direct transitions with 2.28 eV and 2.38 eV band gap energies. Ellipsometry measurements were carried out in the 1.2-6.0 eV spectral region to get information about optical constants, real and imaginary parts of the pseudodielectric function. Moreover, the critical point (CP) analysis of the second derivative spectra of the pseudodielectric constant in the above band gap region was accomplished. The analysis revealed the presence of five CPs with energies of 3.87, 4.16, 4.41, 4.67 and 5.34 eV.Article Citation - WoS: 28Citation - Scopus: 29Annealing Effects on the Structural and Optical Properties of Agin5s8< Thin Films(Elsevier Science Sa, 2008) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringDue to its importance as a perspective material for application in optoelectronic semiconductor devices, the thermal annealing effects on the structural and optical properties of the as-grown vacuum evaporated AgIn5S8 thin films have been investigated. The X-ray data analysis have shown that these films are polycrystalline in nature and exhibit better crystallization with increasing crystallite size and slightly, decreasing unit cell lattice parameter as annealing temperature is raised from 450 to 600 K. The optical energy band gap for the as-grown and thermally annealed films is found to be of direct allowed transitions type. The energy band gap exhibited values of 1.78, 1.74 and 1.62 eV as the samples were annealed at, 450 and 600 K, respectively. This indicates the ability of altering the band gap values of this material by the thermal annealing process. The structural and optical features seem to be suitable for semiconductor device production such as solar cell converters, which has successfully been fabricated by others, metal-insulator-semiconductor (MIS) and metal - oxide - semiconductor (MOS) devices, as well. (c) 2007 Elsevier B.V. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 8Optical Properties of Tl2ingas4< Layered Single Crystal(Elsevier Science Bv, 2007) Qasrawi, A. F.; Gasanly, N. M.The temperature dependence of the optical band gap of Tl2InGaS4 single crystal in the temperature region of 300-500 K and the room temperature refractive index, n(lambda), have been investigated. The absorption coefficient, which was calculated from the transmittance and reflectance spectra in the incident photon energy range of 2.28-2.48 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge corresponds to an indirect allowed transitions energy gap (2.35 eV) that exhibits a temperature coefficient of -4.03 x 10(-4) eV/K. The room temperature n(lambda), calculated from the reflectance and transmittance data, allowed the identification of the oscillator strength and energy, static and lattice dielectric constants, and static refractive index as 16.78 eV and 3.38 eV, 5.96 and 11.77, and 2.43, respectively. (c) 2006 Elsevier B.V. All rights reserved.
