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Article Citation - WoS: 10Citation - Scopus: 11Dispersive Optical Constants of Thermally Deposited Agin5s8< Thin Films(Elsevier Science Sa, 2008) Qasrawi, A. F.Agln(5)S(8) thin films were obtained by the thermal evaporation of Agln(5)S(8) crystals onto ultrasonically cleaned glass substrates. The films are found to exhibit polycrystalline cubic structure. The calculated lattice parameter of the unit cell (a) is 10.78 angstrom. The transmittance data of the as grown films which was recorded at 300 K in the incidence wavelength (lambda) range of 320-1000 nm are used to calculate the refractive, n(lambda). The transmittance and reflectance data are also used to calculate the absorption coefficient of the as grown Agln5S8 thin films. The fundamental absorption edge is found to be corresponding to a direct allowed transitions energy band gap. This band-to-band transition energy is found to be 1.78 eV and it is consistent with that reported for Agln(5)S(8) single crystals. (c) 2007 Elsevier B.V. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Characterization of Pbmo0.3w0.7< Crystal: a Potential Material for Photocatalysis and Optoelectronic Applications(Wiley-v C H verlag Gmbh, 2024) Isik, Mehmet; Gasanly, Nizami MamedPbMo0.3W0.7O4 semiconductor crystal, which contains the balanced ratios of Mo and W, is grown for the first time by Czochralski method. The structural and optical properties of the crystal are investigated in detail in the present study. Structural analysis shows that crystal has tetragonal structure like PbMoO4 and PbWO4 compounds. The optical characteristics are studied by transmission, Raman, FTIR and photoluminescence methods. The bandgap energy is found to be 3.18 eV, and the positions of the conduction and valence bands are determined. The vibrational characteristics are studied by means of Raman and FTIR spectroscopy techniques. Photoluminescence spectrum presents three peaks around 486, 529, and 544 nm which fall into the green emission spectral range. Taking into account the properties of the compound, it is stated that PbMo0.3W0.7O4 (or Pb(MoO4)(0.3)(WO4)(0.7)) has the potential to be used in water splitting applications and optoelectronic devices that emit green light.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: 18Citation - Scopus: 19Temperature Dependence of the Direct Allowed Transitions Band Gap and Optical Constants of Polycrystalline Α-in2se3< Thin Films(Elsevier Science Sa, 2006) Qasrawi, A. F.Polycrystalline alpha-In2Se3 thin films were obtained by the thermal evaporation of alpha-In2Se3 crystals onto glass substrates kept at temperature of 200 degrees C. The temperature dependence of the optical band gap in the temperature region of 300-480 K and the room temperature refractive index, it (lambda), of these films have been investigated. The absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge corresponds to a direct allowed transitions energy gap that exhibits a temperature coefficient of -8.51 x 10(-4) (eV/K). The room temperature n(lambda) which was calculated from the transmittance data allowed the identification of the oscillator strength and energy, static dielectric constant and static refractive index as 20.7 and 2.15 eV, 10.70 and 3.26, respectively. (c) 2006 Elsevier B.V. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 1Hydrogen Implantation Effects on the Electrical and Optical Properties of Inse Thin Films(Tubitak Scientific & Technological Research Council Turkey, 2012) Qasrawi, Atef Fayez; Ilaiwi, Khaled Faysal; Polimeni, AntonioThe effects of hydrogen ion implantation on the structural, electrical and optical properties of amorphous InSe thin films have been investigated. X-ray diffraction analysis revealed no change in the structure of the films. An implantation of 7.3 x 10(18) ions/cm(2) decreased the electrical conductivity by three orders of magnitude at 300 K. Similarly, the conductivity activation energy, which was calculated in the temperature range of 300-420 K, decreased from 210 to 78 meV by H-ion implantation. The optical measurements showed that the direct allowed transitions energy band gap of amorphous InSe films has decreased from 1.50 to 0.97 eV by implantation. Furthermore, significant decreases in the dispersion and oscillator energy, static refractive index and static dielectric constants are also observed by hydrogen implantation.Article Citation - WoS: 9Citation - Scopus: 9Determination of optical parameters of Ga0.75In0.25Se layered crystals(Wiley-v C H verlag Gmbh, 2012) Isik, M.; Gasanly, N. M.The optical properties of the Ga0.75In0.25Se crystals have been investigated by means of transmission and reflection measurements in the wavelength range of 380-1100 nm. The analysis of the results performed at room temperature revealed the presence of optical indirect transtions with band gap energy of 1.89 eV. The variation of the band gap energy as a function of temperature was also studied in the temperature range of 10-300 K. The rate of change of band gap energy (? = 6.2 x 10(4) eV/K) and absolute zero value of the band gap (Egi(0) = 2.01 eV) were reported. The wavelength dependence of the refractive index was analyzed using Wemple and DiDomenico, Sellmeier and Cauchy models to find the oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index values. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Article Citation - WoS: 3Citation - Scopus: 3Enhancement of Nonlinear Optical and Dielectric Properties of Cu2o Films Sandwiched With Indium Slabs(Wiley-v C H verlag Gmbh, 2020) Omar, Ahmad; Qasrawi, Atef F.In this work, the effects of the insertion of indium slabs of thickness 100 nm on the performance of stacked layers of Cu2O are reported. Cu2O/In/Cu2O thin films coated onto ultrasonically cleaned glass substrates are structurally, morphologically, optically, and dielectrically studied. The glassy films of Cu2O display larger, well-ordered grains in an amorphous sea of Cu2O upon insertion of indium slabs between layers of Cu2O. Optically, the indium slabs increase the light absorbability in the IR region by 12.5 times, narrow the energy bandgap, and widen the energy band tails region. They also enhance the nonlinearity in the dielectric response and increase the dielectric constant values by 2.5 times. In addition, the optical conductivity parameters are obtained from the fittings of the dielectric spectra. The analyses reveal an enhancement in the drift mobility, plasmon frequency, and free carrier density via stacking of the indium layer between layers of Cu2O. The drift mobility and plasmon frequency values reach 232.4 cm(2) V-1 s(-1) and 3.95 GHz at a reduced hole-plasmon frequency value of 6.0 x 10(14) Hz (2.48 eV). The values are promising as they indicate the applicability of Cu2O/In/Cu2O interfaces in optoelectronics as thin film transistors and electromagnetic wave cavities.Article Citation - WoS: 10Citation - Scopus: 10Energy Band Gap and Oscillator Parameters of Ga4se3< Single Crystals(Pergamon-elsevier Science Ltd, 2007) Qasrawi, A. F.; Gasanly, N. M.The optical properties of the Bridgman method grown Ga4Se3S crystals have been investigated by means of room temperature, transmittance and reflectance spectral analysis. The optical data have revealed an indirect allowed transition band gap of 2.08 eV. The room temperature refractive index, which was calculated from the reflectance and transmittance data, allowed the identification of the dispersion and oscillator energies, static dielectric constant and static refractive index as 21.08 and 3.85 eV, 6.48 and 2.55, respectively. (C) 2007 Elsevier Ltd. All rights reserved.Article Citation - WoS: 14Citation - Scopus: 14Temperature-Dependent Optical Properties of Gase Layered Single Crystals(Taylor & Francis Ltd, 2016) Isik, M.; Tugay, E.; Gasanly, N. M.Optical properties of GaSe single crystals have been investigated using temperature-dependent transmission and room temperature reflection measurements in the wavelength range of 380-1100nm. The analysis of the absorption data at room temperature showed the existence of indirect transitions in the crystal with energy band gap of 1.98eV. Temperature dependence of the transmission measurements revealed the shift of the absorption edge toward lower energy as temperature is increased from 10 to 280K. The rate of change of the indirect band gap was found as =-6.6x10(-4)eV/K from the analysis of experimental data under the light of theoretical relation giving the band gap energy as a function of temperature. The absolute zero value of the band gap energy and Debye temperature were calculated from the same analysis. The Wemple-DiDomenico single-effective-oscillator model applied to refractive index dispersion data was used to determine the oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index values.Article Citation - WoS: 50Citation - Scopus: 51Elemental Sulfur-Based Polymeric Materials: Synthesis and Characterization(Wiley-blackwell, 2016) Salman, Mohamed Khalifa; Karabay, Baris; Karabay, Lutfiye Canan; Cihaner, AtillaNew elemental sulfur-based polymeric materials called poly(sulfur-random-divinylbenzene) [poly(S-r-DVB)] were synthesized by ring opening polymerization via inverse vulcanization technique in the presence of a mixture of o-, m-, and p-diviniylbenzene (DVB) as a cross-linker. A clear yellow/orange colored liquid was obtained from the elemental sulfur melted at 160 degrees C and then by adding various amounts of DVB to this liquid directly via a syringe at 200 degrees C viscous reddish brown polymeric materials were obtained. The copolymers are soluble in common solvents like tetrahydrofuran, dichloromethane, and chloroform, and they can be coated on any surface as a thin film by a spray coating technique. The characterization of the materials was performed by using nuclear magnetic resonance, fourier transform infrared, and Raman spectroscopies. The morphological properties were monitored via scanning electron microscope technique. Thermal analysis showed that an increase in the amount of DVB in the copolymers resulted in an increase in the thermal decomposition temperature. On the other hand, poly(S-r-DVB) copolymers exhibited good percent transmittance as 50% T between 1500 and 13,000 nm in electromagnetic radiation spectrum, which makes them good candidates to be amenable use in military and surveillance cameras. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43655.
