GCRIS :: Search

Search Results

Now showing 1 - 10 of 41

Citation - WoS: 6
Citation - Scopus: 7
Construction of Self-Assembled Vertical Nanoflakes on Cztsse Thin Films
(Iop Publishing Ltd, 2019) Terlemezoglu, M.; Surucu, O. Bayrakli; Colakoglu, T.; Abak, M. K.; Gullu, H. H.; Ercelebi, C.; Parlak, M.
Cu2ZnSn(S, Se)(4) (CZTSSe) is a promising alternative absorber material to achieve high power conversion efficiencies, besides its property of involving low-cost and earth-abundant elements when compared to Cu(In, Ga) Se-2 (CIGS) and cadmium telluride (CdTe), to be used in solar cell technology. In this study, a novel fabrication technique was developed by utilizing RF sputtering deposition of CZTSSe thin films having a surface decorated with self-assembled nanoflakes. The formation of nanoflakes was investigated by detailed spectroscopic method of analysis in the effect of each stacked layer deposition in an optimized sequence and the size of nanoflakes by an accurate control of sputtering process including film thickness. Moreover, the effects of substrate temperature on the formation of nanoflakes on the film surface were discussed at a fixed deposition route. One of the main advantages arising from the film surface with self-assembled nanoflakes is the efficient light trapping which decreases the surface reflectance. As a result of the detailed production and characterization studies, it was observed that there was a possibility of repeatable and controllable fabrication sequence for the preparation of CZTSSe thin films with self-textured surfaces yielding low surface reflectance.
Citation - WoS: 5
Citation - Scopus: 5
Dispersive Optical Constants of Tl₂ingase_{4< Single Crystals}
(Iop Publishing Ltd, 2007) Qasrawi, A. F.; Gasanly, N. M.
The structural and optical properties of Bridgman method grown Tl2InGaSe4 crystals have been investigated by means of room temperature x-ray diffraction, and transmittance and reflectance spectral analysis, respectively. The x-ray diffraction technique has shown that Tl2InGaSe4 is a single phase crystal of a monoclinic unit cell that exhibits the lattice parameters of a = 0.77244 nm, b = 0.64945 nm, c = 0.92205 nm and beta = 95.03 degrees . The optical data have revealed an indirect allowed transition band gap of 1.86 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 28.51 and 3.45 eV, 9.26 and 3.04, respectively.
Citation - WoS: 5
Citation - Scopus: 5
Structural and Dielectric Performance of the Ba(zn_{1/3< Perovskite Ceramics}
(Iop Publishing Ltd, 2019) Qasrawi, A. F.; Sahin, Ethem Ilhan; Emek, Mehriban; Kartal, Mesut; Kargin, Serdar
In this work, we have explored the antimony doping effects on the structural and dielectric properties of Ba(Zn1/3Nb2/3)O-3 ceramics (BZN). The ceramics displayed perovskite structures with a lattice constant that decreases with increasing Sb content. The antimony solubility limit of the BZN ceramics is x < 0.50. Belowthis limit and in the range of 0.30 <= x <= 0.40, the microstrain, the dislocation density and the stacking faults decreased and the crystallite size increases with increasing Sb content in the composition of BZN. When the limit is exceeded minor phases are predicted by software analysis and confirmed by the experimental techniques. The presence of these phases is also verified by the scanning electron microscopy and energy dispersive x-ray spectroscopy techniques. Increasing the Sb content is observed to decrease the value of the dielectric constant. The Sb doped BZN ceramics exhibits high dielectric quality factors that nominate it for applications in electronics as radio waves resonators.
Citation - WoS: 2
Citation - Scopus: 2
Electron-Lattice Interaction Scattering Mobility in Tl₂ingase_{4< Single Crystals}
(Iop Publishing Ltd, 2008) Qasrawi, A. F.; Gasanly, N. M.
In this work, the dark electrical resistivity, charge carrier density and Hall mobility of Tl(2)InGaSe(4) single crystal have been recorded and analyzed to investigate the dominant scattering mechanism in the crystal. The data analyses have shown that this crystal exhibits an extrinsic n-type conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of two energy levels as 0.396 and 0.512 eV, being dominant above and below 260 K, respectively. The temperature dependence of the carrier density was analyzed by using the single-donor-single-acceptor model. The latter analysis has shown that the above maintained 0.512 eV energy level is a donor impurity level. The compensation ratio for this crystal is determined as 0.96. The Hall mobility of Tl(2)InGaSe(4) is found to be limited by the scattering of electron-acoustic phonon interactions. The calculated theoretical acoustic phonon scattering mobility agrees with the experimental one under the condition that the acoustic deformation potential is 12.5 eV.
Citation - WoS: 15
Citation - Scopus: 16
Electrical Parameters of Al/Inse Rf Sensors
(Iop Publishing Ltd, 2014) Qasrawi, A. F.
An Al/InSe/C Schottky device is designed on the surface of amorphous InSe thin films. The device is observed to exhibit a switching property at particular biasing voltages. The 'on/off' current ratio is found to be 7.9 and 9.3 at forward and reverse biasing voltages of 2.0 and 2.25 V, respectively. The 'off' and 'on' operational modes are ascribed to the domination of the tunneling of charged particles through a barrier height of 0.83 eV with a depletion region width of 64 nm and due to the domination of the thermionic emission of charged carriers over a barrier height of 0.53 eV, respectively. In addition, the spectral analysis of the capacitance of the device which was carried in the frequency range of 10.0 k-3.0 GHz reflected dc voltage biasing-dependent high quality resonating peaks. The strongest one appeared at a frequency of 36.8 MHz for a biasing voltage of 0.70 V. Furthermore, the loss tangent of the Al/InSe/C device is found to be of the order of 10(-7) at 3.0 GHz. Consistently, the capacitance-voltage spectra of these sensors reflected pronounced tunability up to 100 MHz. The Al/InSe/C device performance, the switching properties and the quality of the resonance peaks indicate the possibility of using these sensors in RF technology.
Citation - WoS: 3
Citation - Scopus: 3
Optoelectronic Properties of Ga₄se_{3< 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).
Citation - WoS: 40
Citation - Scopus: 42
Design and Electrical Performance of Cds/Sb_{2< 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.
Citation - WoS: 23
Citation - Scopus: 24
First 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 Huseyin
The 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.
Citation - WoS: 5
Citation - Scopus: 5
Growth 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.
Citation - WoS: 7
Citation - Scopus: 7
Phase-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.

Filters

Settings

Sort By

Results per page

Search Results