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Article Citation - WoS: 1Citation - Scopus: 1Photovoltaic Effect and Space Charge Limited Current Analysis in Tlgate2 Crystals(Polish Acad Sciences inst Physics, 2012) Qasrawi, A. F.; Yaseen, T. R.; Eghbariy, B.; Gasanly, N. M.Anisotropic space charge limited current density analysis and photovoltaic effect in TlGaTe2 single crystals has been investigated. It is shown that, above 330 K, the crystal exhibits intrinsic and extrinsic type of conductivity along (c-axis) and perpendicular (a-axis) to the crystal's axis, respectively. The current density (J) is found to be space charge limited. It is proportional to the square and three halves power of voltage (V) along the a- and c-axis, respectively. Along the a-axis and at sufficiently low electric field values, the activation energy of the current density is found to depend on the one half power of electric field. At high electric fields, the activation energy is field invariant. This behavior is found to be due to the Pool Frenkel effect and due to a trap set located at 0.26 eV, respectively. Along the c-axis the crystal is observed to operate under the Child Langmuir space charge limited regime. TlGaTe2 crystals are found to exhibit photovoltaic properties. The open circuit photovoltage is recorded as a function of illumination intensity at room temperature.Article Citation - WoS: 6Citation - Scopus: 6Low-Temperature Thermo Luminescence Studies on Tlins2 Layered Single Crystals(Polish Acad Sciences inst Physics, 2014) Isik, M.; Delice, S.; Gasanly, N. M.Thermoluminescence characteristics of TlInS2 layered single crystals grown by the Bridgman method were investigated in the low temperature range of 10-300 K. The illuminated sample with blue light (approximate to 470 nm) at 10 K was heated at constant heating rate. Curve fitting, initial rise and various heating rate methods were used to determine the activation energy of the trap levels. All applied methods showed good consistency about the presence of five trapping centers located at 14, 19, 350, 420, and 520 meV. Behavior of the TL curve for various heating rates was investigated. Traps distribution has also been studied. The activation energies of the distributed trapping centers were found to be increasing from 14 to 46 meV.Article Citation - WoS: 15Citation - Scopus: 15Deep Traps Distribution in Tlins2 Layered Crystals(Polish Acad Sciences inst Physics, 2009) Isik, M.; Gasanly, N. M.; Ozkan, H.The trap centers and distributions in TlInS2 were studied in the temperature range of 100-300 K by using thermally stimulated currents technique. Experimental evidence was found for the presence of three trapping centers with activation energies 400, 570, and 650 meV. Their capture cross-sections were determined as 6.3 x 10(-16), 2.7 x 10(-12), and 1.8 x 10(-11) cm(2), respectively. It was concluded that in these centers retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. An exponential distribution of hole traps was revealed from the analysis of the thermally stimulated current data obtained at different light excitation temperatures. This experimental technique provided a value of 800 meV/decade for the trap distribution.Article Citation - WoS: 5Citation - Scopus: 5Revealing Defect Centers in Pbwo4 Single Crystals Using Thermally Stimulated Current Measurements(Aip Publishing, 2024) Isik, M.; Gasanly, N. M.The trap centers have a significant impact on the electronic properties of lead tungstate (PbWO4), suggesting their crucial role in optoelectronic applications. In the present study, we investigated and revealed the presence of shallow trap centers in PbWO4 crystals through the utilization of the thermally stimulated current (TSC) method. TSC experiments were performed in the 10-280 K range by applying a constant heating rate. The TSC spectrum showed the presence of a total of four peaks, two of which were overlapped. As a result of analyzing the TSC spectrum using the curve fit method, the activation energies of revealed centers were found as 0.03, 0.11, 0.16, and 0.35 eV. The trapping centers were associated with hole centers according to the comparison of TSC peak intensities recorded by illuminating the opposite polarity contacts. Our findings not only contribute to the fundamental understanding of the charge transport mechanisms in PbWO4 crystals but also hold great promise for enhancing their optoelectronic device performance. The identification and characterization of these shallow trap centers provide valuable insights for optimizing the design and fabrication of future optoelectronic devices based on PbWO4.Article Compositional Dependence of Optical Modes Frequencies in T1gax< Layered Mixed Crystals (0 ≤ x ≤ 1)(Polish Acad Sciences inst Physics, 2014) Isik, M.; Gasanly, N. M.; Korkmaz, F.The infrared transmittance and Raman scattering spectra in TlGaxIn1-xS2 (0 <= x <= 1) layered mixed crystals grown by the Bridgman method were studied in the frequency ranges of 400-2000 and 250-400 cm(-1), respectively. The bands observed at room temperature in IR transmittance spectra of TlGaxIn1-xS2 were interpreted in terms of multiphonon absorption processes. The dependences of the frequencies of IR- and Raman-active modes on the composition of TlGaxIn1-xS2 mixed crystals were also established. The structural characterization of the mixed crystals was investigated by means of X-ray diffraction measurements and compositional dependence of lattice parameters was revealed.Article Analysis of Thermoluminescence Glow Peaks in Β-Irradiated Tlgases Crystals(Polish Acad Sciences inst Physics, 2016) Isik, M.; Yildirim, T.; Gasanly, N. M.Thermoluminescence properties of TlGaSeS layered single crystals were investigated in the temperature range of 280-720 K. Thermoluminescence glow curve exhibited three peaks with maximum temperatures of approximate to 370, 437, and 490 K. Curve fitting, initial rise and peak shape methods were used to determine the activation energies of the trapping centers. All applied methods resulted with energies around 0.82, 0.91, and 0.99 eV. Dose dependence of the thermoluminescence intensity was also examined for the doses in the range of 0.7-457.6 Gy. Peak maximum intensity of the observed peak around 370 K showed an increase up to a certain dose and then a decrease at higher doses. This non-monotonic dose dependence was discussed under the light of a reported model in which different kinds of competition between radiative and nonradiative recombination centers during excitation or heating stages of the thermoluminescence process are explained.Article Citation - WoS: 5Citation - Scopus: 5Dielectric and photo-dielectric properties of TlGaSeS crystals(indian Acad Sciences, 2014) Qasrawi, A. F.; Abu-Zaid, Samah F.; Ghanameh, Salam A.; Gasanly, N. M.The room temperature, dark and photo-dielectric properties of the novel crystals TlGaSeS are investigated in the frequency, intensity and biasing voltage having ranges of similar to 1-120 MHz, 14-40 klux and 0-1 V, respectively. The crystals are observed to exhibit a dark high frequency effective dielectric constant value of similar to 10.65 x 10(3) with a quality factor of similar to 8.84 x 10(4) at similar to 120 MHz. The dielectric spectra showed sharp resonance-antiresonance peaks in the frequency range of similar to 25-250 kHz. When photoexcited, pronounced increase in the dielectric constant and in the quality factor values with increasing illumination intensity are observed. Signal amplification up to similar to 33% with improved signal quality up to similar to 29% is attainable via photoexcitation. On the other hand, the illuminated capacitance voltage characteristics of the crystals reflected a downward shift in the voltage biasing and in the built-in voltage of the device that is associated with increase in the uncompensated carrier density. The increase in the dielectric constant with increasing illumination intensity is ascribed to the decrease in the crystal's resistance as a result of increased free carrier density. The light sensitivity of the crystals, the improved dielectric properties and the lower biasing voltage obtained via photoexcitation and the well-enhanced signal quality factor of the crystals make them promising candidates for optical communication systems.Article Citation - WoS: 13Citation - Scopus: 13Thermally Assisted Variable Range Hopping in Tl4s3< Crystal(indian Acad Sciences, 2015) Ziqan, Abdelhalim M.; Qasrawi, A. F.; Mohammad, Abdulftah H.; Gasanly, N. M.In this study, a modified model for the application of the thermionic and hopping current conduction mechanisms in the presence of continuous mixed conduction is investigated, discussed, experimented and simulated. It is observed that there exists a contribution from the hopping conductivity to the total conduction even at temperature ranges where the thermionic emission is mainly dominant. The contribution weight of a specific mechanism at particular temperature range is estimated. In addition, a modification to the Mott's variable range hopping (VRH) transport parameters like density of localized state near the Fermi level, the average hopping range and the hopping energy in the presence of mixed conduction mechanism is also reported. This new approach corrects the evaluated electrical parameters that are necessary for the construction of electronic devices like absorption layers in solar cells. This proposed model is also used to explain the conduction mechanism and investigate the electrical conduction thermionic and Mott's VRH parameters in Tl4S3Se crystals and in CuAlO2 thin films.
