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Article Citation - WoS: 5Citation - Scopus: 5Growth and Temperature Tuned Band Gap Characteristics of Nabi(moo4)2< Single Crystal(Iop Publishing Ltd, 2023) Isik, M.; Guler, I; Gasanly, N. M.Structural and optical properties of double sodium-bismuth molybdate NaBi(MoO4)(2) semiconductor compound was investigated by x-ray diffraction, Raman and transmission experiments. From the x-ray diffraction experiments, the crystal that has tetragonal structure was obtained. Vibrational modes of the crystal were found from the Raman experiments. Transmission experiments were performed in the temperature range of 10-300 K. Derivative spectroscopy analysis and absorption spectrum analysis were performed to get information about the change in band gap energy of the crystal with temperature. It was observed that the band gap energies of the crystal at different temperatures obtained from these techniques are well consisted with each other. By the help of absorption spectrum which was obtained from transmission measurements performed at varying temperatures, absolute zero value of the band gap and average phonon energy as 3.03 +/- 0.02 eV and Eph = 24 +/- 0.2 meV, respectively. Moreover, based on absorption spectrum analysis the Urbach energy of the crystal was obtained as 0.10 eV.Article Citation - WoS: 7Citation - Scopus: 7Phase-dependent characteristics of a superconducting junction by using the Schrodinger wave function(Iop Publishing Ltd, 2007) Canturk, M.; Kurt, E.As a macroscopic quantum system, superconducting junction devices are considered both analytically and numerically with the help of the Schrodinger wave equation. Considering the Cooper pair wave function psi in a time-dependent nature, the Hamiltonian of the system is constructed. The phase difference theta is assumed to be a unique independent variable of the superconducting junction in order to evaluate the characteristics of the system. The probability rho(theta) and super current j(theta) densities are determined for different applied voltages V. It is observed that both the amplitude and the period of the wave function psi(theta) have indicated different behaviors as functions of theta for various cases of V. Similarly, rho and j reflect drastic changes. It is shown that numerical results are in good agreement with the analytic results. Our results indicate consistency with some earlier experimental studies for different superconducting devices.Article Citation - WoS: 14Citation - Scopus: 13Light Illumination Effect on the Electrical and Photovoltaic Properties of In6s7< Crystals(Iop Publishing Ltd, 2006) Qasrawi, AF; Gasanly, NMThe electrical and photoelectrical properties of In6S7 crystals have been investigated in the temperature regions of 170-300 K and 150-300 K, respectively. The dark electrical analysis revealed the intrinsic type of conduction. The energy band gap obtained from the temperature-dependent dark current is found to be 0.75 eV. It is observed that the photocurrent increases in the temperature range of 150 K up to T-m = 230 K and decreases at T > T-m. Two photoconductivity activation energies of 0.21 and 0.10 eV were determined for the temperature ranges below and above Tm, respectively. The photocurrent (I-ph)-illumination intensity (F) dependence follows the law I-ph alpha F-gamma. The value of. decreases when the temperature is raised to T-m, then it starts increasing. The change in the value. with temperature is attributed to the exchange in role between the recombination and trapping centres in the crystal. The crystals are found to exhibit photovoltaic properties. The photovoltage is recorded as a function of illumination intensity at room temperature. The maximum open-circuit voltage and short-circuit photocurrent density, which are related to an illumination intensity equivalent to one sun, are 0.12 V and 0.38 mA cm(-2), respectively.Article Citation - WoS: 14Citation - Scopus: 15Induced Scattering Limits on Fast Radio Bursts From Stellar Coronae(Iop Publishing Ltd, 2016) Lyubarsky, Yuri; Ostrovska, SofiyaThe origin of fast radio bursts remains a puzzle. Suggestions have been made that they are produced within the Earth's atmosphere, in stellar coronae, in other galaxies, or at cosmological distances. If they are extraterrestrial, the implied brightness temperature is very high, and therefore the induced scattering places constraints on possible models. In this paper, constraints are obtained on flares from coronae of nearby stars. It is shown that the radio pulses with the observed power could not be generated if the plasma density within and in the nearest vicinity of the source is as high as is necessary to provide the observed dispersion measure. However, one cannot exclude the possibility that the pulses are generated within a bubble with a very low density and pass through the dense plasma only in the outer corona.Article Citation - WoS: 3Citation - Scopus: 3Optoelectronic Properties of Ga4se3< Single Crystals(Iop Publishing Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.; Ilaiwi, K. F.The optoelectronic properties of Bridgman method-grown Ga(4)Se(3)S single crystals have been investigated by means of room temperature electrical resistivity, temperature-dependent photosensitivity and temperature-dependent optical absorption. The photosensitivity was observed to increase with decreasing temperature, the illumination dependence of which was found to exhibit monomolecular recombination in the bulk at 300 K. The absorption coefficient, which was calculated in the incident photon energy range of 2.01-2.35 eV, increased with increasing temperature. Consistently, the absorption edge shifts to lower energy values. The fundamental absorption edge corresponds to an indirect allowed transitions energy gap (2.08 eV at 300 K) that exhibits a temperature coefficient of -95 x 10(-4) eVK(-1).Article Citation - WoS: 40Citation - Scopus: 42Design and Electrical Performance of Cds/Sb2< Tunneling Heterojunction Devices(Iop Publishing Ltd, 2018) Khusayfan, Najla M.; Qasrawi, A. F.; Khanfar, Hazem K.In the current work, a tunneling barrier device made of 20 nm thick Sb2Te3 layer deposited onto 500 nm thick CdS is designed and characterized. The design included a Yb metallic substrate and Ag point contact of area of 10(-3) cm(2). The heterojunction properties are investigated by means of x-ray diffraction and impedance spectroscopy techniques. It is observed that the coating of the Sb2Te3 onto the surface of CdS causes a further deformation to the already strained structure of hexagonal CdS. The designed energy band diagram for the CdS/Sb2Te3 suggests a straddling type of heterojunction with an estimated conduction and valence band offsets of 0.35 and 1.74 eV, respectively. In addition, the analysis of the capacitance-voltage characteristic curve revealed a depletion region width of 14 nm. On the other hand, the capacitance and conductivity spectra which are analyzed in the frequency domain of 0.001-1.80 GHz indicated that the conduction in the device is dominated by the quantum mechanical tunneling in the region below 0.26 GHz and by the correlated barrier hopping in the remaining region. While the modeling of the conductivity spectra allowed investigation of the density of states near Fermi levels and an average scattering time of 1.0 ns, the capacitance spectra exhibited resonance at 0.26 GHz followed by negative differential capacitance effect in the frequency domain of 0.26-1.8 GHz. Furthermore, the evaluation of the impedance and reflection coefficient spectra indicated the usability of these devices as wide range low pass filters with ideal values of voltage standing wave ratios.Article Citation - WoS: 25Citation - Scopus: 25First Principles Study on the Structural, Electronic, Mechanical and Lattice Dynamical Properties of Xrhsb (x = Ti and Zr) Paramagnet Half-Heusler Antimonides(Iop Publishing Ltd, 2019) Surucu, Gokhan; Candan, Abdullah; Erkisi, Aytac; Gencer, Aysenur; Gullu, Hasan HuseyinThe half-Heusler TiRhSb and ZrRhSb alloys in the formation of face-centered cubic MgAgAs-type structure, which conforms to the F (4) over bar 3m space group with 216 as the space number, have been investigated using Generalized Gradient Approximation (GGA) implemented in Density Functional Theory (DFT). The calculated formation enthalpies and the plotted energy-volume curves of different types of structural phases (alpha, beta, and gamma) in these alloys indicate that the gamma-phase structure is the best energetically suitable structure. In addition, TiRhSb and ZrRhSb alloys have been found as paramagnetic (PM) with the investigation of antiferromagnetic (AFM), ferromagnetic (FM), and paramagnetic (PM) orders in the most stable gamma-phase structure. Therefore, their electronic, mechanical, and dynamical properties have been examined in the gamma structural phase and paramagnetic order. These alloys have semiconducting nature due to the observed same band gaps in both the majority and minority spin channels of the calculated spin-polarised electronic band structure. These calculated band gaps are 0.75 eV for gamma-TiRhSb and 1.18 eV for gamma-ZrRhSb. The predicted elastic constants indicate that the alloys in this study are mechanically stable and show nearly isotropic behavior in the gamma structural phase. Also, the minimum and the diffuson thermal conductivites have been determined for these alloys. Finally, the calculated phonon dispersion spectras for the gamma-TiRhSb and gamma-ZrRhSb half-Heusler antimonide alloys show the dynamic stability of these systems.Article Citation - WoS: 3Citation - Scopus: 2Performance Enhancement of Silicon Photodiodes Through the Integration of Green Synthesized Reduced Graphene Oxide Variants(Iop Publishing Ltd, 2024) Yildiz, D. E.; Sürücü, Özge; Surucu, O.; Balaban, H. Mert; Bilici, I; Yildirim, M.; Sürücü, Özge; Mert Balaban, H.; Electrical-Electronics Engineering; Electrical-Electronics EngineeringThis study examines the potential of enhancing the optoelectronic properties of silicon photodiodes by producing and analyzing heterostructures that incorporate reduced graphene oxide (rGO) synthesized with silicon using different reduction methods. Graphene oxide (GO) was manufactured utilizing an enhanced Hummers' method. Subsequently, reduced graphene oxides (rGOs) were made by chemical and thermal reduction processes, which are considered ecologically friendly. The use of ascorbic acid to produce ascorbic acid-reduced graphene oxide (ArGO) and thermal processing to produce thermally reduced graphene oxide (TrGO) have significantly contributed to the development of high-performance photodiode technology. The electrical properties were carefully assessed under different levels of light, revealing the substantial impact of integrating reduced graphene oxides (rGOs) on the performance of the diodes. Comparing ArGO/Si, TrGO/Si, and GO/Si heterostructures shows that customized rGO has the potential to greatly influence the responsivity and efficiency of Si-based optoelectronic devices, making a significant contribution to photodiode technology.Article Citation - WoS: 4Citation - Scopus: 5Znse/Al Nanosandwiched Structures as Dual Terahertz-Gigahertz Signal Receivers(Iop Publishing Ltd, 2019) Qasrawi, A. F.; Alsabe, Ansam M.In the current work, we focus on the enhancements in performance of the ZnSe terahertz/gigahertz signal receivers which are achieved by the insertion of nanosheets of Al layers of thickness of 30 nm between two 500 nm thick layers of ZnSe. The Al nanosandwiching which decreased the defect density, stacking faults and increased the grain size in the films increased the optical conductivity by more than 125%, increased the drift mobility to 313 cm(2) V-1 s(-1) and widens the plasmon frequency ranges to 0.49-4.92 GHz. In addition, the analysis of the terahertz cutoff (f(co)) frequency spectra have shown that the presence of Al nanosheets improves the cutoff frequency value by three orders of magnitude making the ZnSe receivers more suitable for visible light and IR communication technology. The value of f(co) is 49.6 THz when light signal of wavelengths of 408 nm that suits blue lasers is irradiated. Moreover, the impedance spectroscopy analysis in the gigahertz frequency domain has shown that the Al sandwiched ZnSe exhibits negative capacitance spectra in the frequency domain of 0.01-1.04 GHz. This property is useful for parasitic capacitance cancelling and noise reducing in circuits. Furthermore, the study of the microwave cutoff frequency spectra has shown that the value of f(co) is enhanced by three orders of magnitude above 1.5 GHz.Article Citation - WoS: 25Citation - Scopus: 24Preparation of Electrospun Pcl-Based Scaffolds by Mono/Multi-functionalized Go(Iop Publishing Ltd, 2019) Basar, Ahmet Ozan; Sadhu, Veera; Sasmazel, Hilal Turkoglu; Turkoglu Sasmazel, HilalIn the present study, sythetic biodegradable polymer poly(epsilon-caprolactone) (PCL) and graphene oxide (GO) were combined together to prepare 3D, composite tissue scaffolds (PCL/GO scaffolds) by using electrospinning technique. Also, the influence of Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) and/or thiophene (Th) modified GO on the composite PCL/GO mats (PCL/GO, PCL/GO-GRGDSP, PCL/ GO-Th, PCL/GO-GRGDSP-Th) was further investigated. Characteristic examinations of the scaffolds were carried out by scanning electron microscope (SEM), contact angle (CA) measurements, x-ray photoelectron spectroscopy, TGA, electrical conductivity tests, phosphate buffer saline absorption and shrinkage tests and mechanical tests. All of the scaffolds were exhibited suitable bead free and uniform morphology according to SEM images. With the addition of GO, better hydrophilicity and a slight CA decrease (similar to 5 degrees) for the PCL/GO scaffolds were observed. Mechanical properties were reinforced drastically with the addition and well-dispersion of GO into PCL matrix. The incorporation of PCL and GO exhibited enhanced electrical conductivity and the highest value was found for PCL/GO-GRGDSP-Th (2%) as 15.06 mu S cm(-1). The MG-63 osteoblast cell culture studies (MTT assay, ALP activity, Alizarin-Red staining, fluorescence and SEM analyses) showed that PCL/GO-GRGDSP-Th (1%) scaffolds exhibited the highest biocompatibility performance (1.87 fold MTT absorbance value comparing with neat PCL) due to the advanced properties of GO and the biological interfaces.
