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Article Citation - WoS: 11Citation - Scopus: 12Structural, optical, electrical and dielectric properties of Bi1.5Zn0.92Nb1.5-xNixO6.92-3x/2 solid solution(Taylor & Francis Ltd, 2012) Qasrawi, A. F.; Nazzal, E. M.; Mergen, A.The effects of Ni content on the structural, optical, dielectric and electrical properties of Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics have been investigated. Nickel atoms were inserted into pure samples in accordance to the composition Bi1.5Zn0.92Nb1.5-xNixO6.92-3x/2, with x varying from 0.07 to 0.40. The structural analysis revealed that a single phase of the pyrochlore compound can be obtained for x values of 0.07 and 0.10 only. Further increase in Ni caused the appearance of multiple phases. The optical energy band gaps are determined as 3.30, 3.35 and 3.52 eV for Ni content of 0.00, 0.07 and 0.10 respectively. The temperature dependent electrical resistivity and the frequency dependent capacitance are observed to increase with increasing Ni content. The resonance frequency, which was determined from the capacitance-frequency dependence, was observed to shift from 12.14 to 10.47 kHz as the x values increase from 0.00 to 0.10 respectively.Article Citation - WoS: 8Citation - Scopus: 9Structural and Optoelectronic Properties of Cds/Y Thin Films(Elsevier Science Sa, 2019) Qasrawi, A. F.; Abed, Tamara Y.In the current study, the structural, optical, photoelectrical and electrical properties of CdS/Y/CdS thin films are investigated. The current design include the evaporation of a layer of 70 nm thick yttrium between two layers of CdS. Each CdS layer is of thickness of 500 nm. It is observed that the yttrium slab increased the microstrain, defect density, stacking faults and decreased the grain size and redshifts the indirect allowed transitions energy band gap of CdS. In addition an enhancement by similar to 5 times in the light absorbability is detected at 1.74 eV. The enhanced absorbance results in increasing the photocurrent by similar to 21 times and changed the recombination mechanism from a trap assisted recombination to supralinear recombination mechanisms. Moreover, the ac signal analysis in the frequency domain of 10-1800 MHz has shown that the yttrium forces the CdS to exhibit negative capacitance effect and make it behave as band stop filter with notch frequency of 1520 MHz. The quality of the CdS/Y/CdS films as microwave cavities are screened by the evaluation of the return loss which revealed good features of the nanostructured films as microwave receivers.Article Citation - WoS: 4Citation - Scopus: 4Thermally Controlled Band Gap Tuning in Cuo Nano Thin Films for Optoelectronic Applications(indian Assoc Cultivation Science, 2024) Delice, S.; Isik, M.; Gasanly, N. M.Temperature dependency of band gap in CuO nano thin films has been investigated by virtue of transmission experiments at different temperatures. Structural and morphological characterization were achieved using X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Analysis on the XRD diffractogram revealed the presence of monoclinic structure for the CuO. Average crystallite size was determined as 17.8 nm. Absorption characteristics in between 10 and 300 K were presented in the wavelength range of 360-1100 nm. The band gap of the CuO was found to be similar to 2.17 eV at 300 K using Tauc and spectral derivative methods. This value increased to similar to 2.24 eV at 10 K. Both methods showed that the band gap extended with decreasing temperature. Temperature dependency of the band gap was studied using Varshni relation. The band gap at absolute temperature, variation of the band gap with temperature and Debye temperature were calculated as 2.242 +/- 0.002 eV, - 5.4 +/- 0.2 x 10(-4) eV/K and 394 +/- 95 K, respectively.Article Citation - WoS: 10Citation - Scopus: 10Temperature effects on the optoelectronic properties of AgIn5S8 thin films(Elsevier Science Sa, 2011) Qasrawi, A. F.Polycrystalline AgIn5S8 thin films are obtained by the thermal evaporation of AgIn5S8 crystals onto ultrasonically cleaned glass substrates under a pressure of similar to 1.3 x 10(-3) Pa. The temperature dependence of the optical band gap and photoconductivity of these films was studied in the temperature regions of 300-450 K and 40-300 K, respectively. The heat treatment effect at annealing temperatures of 350, 450 and 550 K on the temperature dependent photoconductivity is also investigated. The absorption coefficient, which was studied in the incidence photon energy range of 1.65-2.55 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge which corresponds to a direct allowed transition energy band gap of 1.78 eV exhibited a temperature coefficient of -3.56 x 10(-4) eV/K. The 0 K energy band gap is estimated as 1.89 eV. AgIn5S8 films are observed to be photoconductive. The highest and most stable temperature invariant photocurrent was obtained at an annealing temperature of 550 K. The photoconductivity kinetics was attributed to the structural modifications caused by annealing and due to the trapping-recombination centers' exchange. (C) 2010 Elsevier B.V. All rights reserved.Article Citation - WoS: 25Citation - Scopus: 25Temperature-Tuned Band Gap Properties of Mos2 Thin Films(Elsevier, 2020) Surucu, O.; Isik, M.; Gasanly, N. M.; Terlemezoglu, M.; Parlak, M.MoS2 is one of the fascinating members of transition metal dichalcogenides and has attracted great attention due to its various optoelectronic device applications and its characteristic as two-dimensional material. The present paper reports the structural and temperature tuned optical properties of MoS2 thin films grown by RF magnetron sputtering technique. It was observed that the atomic composition ratio of Mo:S was nearly equal to 1:2 and the deposited thin films have hexagonal crystalline structure exhibiting Raman peaks around 376 and 410 cm(-1). The band gap energies were determined as 1.66 and 1.71 eV at 300 and 10 K, respectively and temperature dependency of band gap energy was analyzed by means of Varshni and O'Donnell-Chen models. (C) 2020 Elsevier B.V. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 7Optical Properties of Gas Crystals: Combined Study of Temperature-Dependent Band Gap Energy and Oscillator Parameters(Natl inst Science Communication-niscair, 2017) Isik, Mehmet; Tugay, Evrin; Gasanly, Nizami; Department of Electrical & Electronics EngineeringOptical parameters of gallium sulfide (GaS) layered single crystals have been found through temperature-dependent transmission and room temperature reflection experiments in the wavelength range of 400-1100 nm. Experimental data demonstrates the coexistence of both optical indirect and direct transitions and the shift of the absorption edges toward lower energies by increasing temperature in the range of 10-300 K. Band gap at zero temperature, average phonon energy and electron phonon coupling parameter for indirect and direct band gap energies have been obtained from the analyses of temperature dependences of band gap energies. At high temperatures kT>> (E-ph), rates of band gap energy change have been found as 0.56 and 0.67 me V/K for E-gi and E-gd, respectively. Furthermore, the dispersion of refractive index has been discussed in terms of the Wemple-DiDomenico single effective oscillator model. The refractive index dispersion parameters, namely oscillator and dispersion energies, oscillator strength and zero-frequency refractive index, have been found to be 4.48 eV, 24.8 eV, 6.99x10(13) m(-2) and 2.56, respectively. The results of the present work will provide an important contribution to the research areas related to the characterization and optoelectronic device fabrication using GaS layered crystals.Conference Object Citation - WoS: 4Citation - Scopus: 3Temperature-dependent material characterization of CuZnSe2 thin films(Elsevier Science Sa, 2020) Gullu, H. H.; Surucu, O.; Terlemezoglu, M.; Isik, M.; Ercelebi, C.; Gasanly, N. M.; Parlak, M.In the present work, CuZnSe2 (CZSe) thin films were co-deposited by magnetron sputtering of ZnSe and Cu targets. The structural analyses resulted in the stoichiometric elemental composition and polycrystalline nature without secondary phase contribution in the film structure. Optical and electrical properties of CZSe thin films were investigated using temperature-dependent optical transmission and electrical conductivity measurements. The band gap energy values were obtained using transmittance spectra under the light of expression relating absorption coefficient to incident photon energy. Band gap energy values were found in decreasing behavior from 2.31 to 2.27 eV with increase in temperature from 10 to 300 K. Temperature-band gap dependency was evaluated by Varshni and O'Donnell models to detail the optical parameters of the thin films. The experimental dark and photoconductivity values were investigated by thermionic emission model over the grain boundary potential. Room temperature conductivity values were obtained in between 0.91 and 4.65 ( x 10(-4) Omega(-1)cm(-1)) under various illumination intensities. Three different linear conductivity regions were observed in the temperature dependent profile. These linear regions were analyzed to extract the activation energy values.Article Citation - WoS: 2Citation - Scopus: 2Anisotropic Electrical and Dispersive Optical Parameters in Ins Layered Crystals(Pergamon-elsevier Science Ltd, 2010) Qasrawi, A. F.; Gasanly, N. M.The anisotropy effect on the current transport mechanism and on the dispersive optical parameters of indium monosulfide crystals has been studied by means of electrical conductivity and polarized reflectance measurements along the a-axis and the b-axis, respectively. The temperature-dependent electrical conductivity analysis in the range 10-350 K for the a-axis and in the range 30-350 K for the b-axis revealed the domination of the thermionic emission of charge carriers and the domination of variable range hopping above and below 100 K, respectively. At high temperatures (T > 100 K) the conductivity anisotropy, s, decreased sharply with decreasing temperature following the law s proportional to exp(-E(s)/kT). The anisotropy activation energy, E(s), was found to be 330 and 17 meV above and below 220 K, respectively. Below 100 K, the conductivity anisotropy is invariant with temperature. in that region, the calculated hopping parameters are altered significantly by the conductivity anisotropy. The optical reflectivity analysis in the wavelength range 250-650 nm revealed a clear anisotropy effect on the dispersive optical parameters. In particular, the static refractive index, static dielectric constant, lattice dielectric constant, dispersion energy and oscillator energy exhibited values of 2.89, 8.39, 19.7, 30.02 eV and 4.06 eV, and values of 2.76, 7.64, 25.9, 22.26 eV and 3.35 eV for light polarized along the a-axis and the b-axis, respectively. (C) 2009 Elsevier Ltd. All rights reserved.
