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Citation - WoS: 7
Citation - Scopus: 7
Trapping Centers and Their Distribution in Tl₂ga_{2< Layered Single Crystals}
(Pergamon-elsevier Science Ltd, 2009) Isik, M.; Gasanly, N. M.
Thermally stimulated current (TSC) measurements with current flowing perpendicular to the layers were carried out on Tl2Ga2Se3S layered single crystals in the temperature range of 10-260K. The experimental data were analyzed by using different methods, such as curve fitting, initial rise and isothermal decay methods. The analysis revealed that there were three trapping centers with activation energies of 12, 76 and 177 meV. It was concluded that retrapping in these centers was negligible, which was confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. The capture cross section and the concentration of the traps have been also determined. An exponential distribution of electron traps was revealed from the analysis of the TSC data obtained at different light illumination temperatures. This experimental technique provided values of 10 and 88 meV/decade for the traps distribution related to two different trapping centers. (C) 2009 Elsevier Ltd. All rights reserved.
Citation - WoS: 5
Citation - Scopus: 5
Thermoluminescence Properties of Al Doped Zno Nanoparticles
(Elsevier Sci Ltd, 2018) Isik, M.; Gasanly, N. M.
ZnO nanoparticles doped with aluminum (AZO nanoparticles) were investigated using low temperature thermoluminescence (TL) and structural characterization experiments. TL experiments were performed on AZO nanoparticles in the temperature range of 10-300 K. TL curve presented one intensive peak around 123 K and two overlapped peaks to intensive peak around 85 and 150 K for heating rate of 0.1 K/s. Curve fitting and initial rise methods were used to find the activation energies of associated trapping centers. Analyses resulted in the presence of three centers at 0.05, 0.08 and 0.17 eV with peak maximum temperatures (T-m) of 86.2, 121.5 and 147.1 K, respectively. TL experiments were expanded using different heating rates between 0.1 K/s and 0.5 K/s. Behavior of revealed traps was investigated using an experimental technique called as T-m - T-stop method. It was seen that traps are quasi-continuously distributed within the band gap. Structural properties were studied using x-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy experiments.
Citation - WoS: 8
Citation - Scopus: 8
Thermoluminescence Properties of Zno Nanoparticles in the Temperature Range 10-300 K
(Springer, 2016) Isik, M.; Yildirim, T.; Gasanly, N. M.
Low-temperature thermoluminescence (TL) properties of ZnO nanoparticles grown by sol-gel method were investigated in the 10-300 K temperature range. TL glow curve obtained at 0.2 K/s constant heating rate exhibited one broad peak around 83 K. The observed peak was analyzed using curve fitting method to determine the activation energies of trapping center(s) responsible for glow curve. Analyses resulted in the presence of three peaks at 55, 85 and 118 K temperatures with activation energies of 12, 30 and 45 meV, respectively. Thermal cleaning process was applied to separate overlapped peaks and get an opportunity to increase the reliability of results obtained from curve fitting method. Heating rate dependence of glow curve was also studied for rates between 0.2 and 0.7 K/s. The shift of the peak maximum temperatures to higher values and decrease in peak height with heating rate were observed. Moreover, X-ray diffraction and scanning electron microscopy were used for structural characterization.
Low Temperature Thermoluminescence of Quaternary Thallium Sulfide Tl₄inga_3<
(indian Assoc Cultivation Science, 2015) Delice, S.; Isik, M.; Bulur, E.; Gasanly, N. M.
Thermoluminescence measurements have been carried out on Tl4InGa3S8 single crystals in the temperature range of 10-300 K at various heating rates. The observed thermoluminescence spectra have been analyzed applying many methods like curve fitting, initial rise, peak shape and heating rate methods. Thermal cleaning method has been performed on the observed thermoluminescence glow curve to separate the overlapped peaks. Three distinctive trapping centers with activation energies of 13, 44 and 208 meV have been revealed from the results of the analysis. Heating rate dependence and traps distribution investigations have been also undertaken on the most intensive peak. The thermoluminescence mechanisms in the observed traps have been attributed to first order kinetics (slow retrapping) on the strength of the consistency between theoretical assumptions for slow retrapping process and experimental outcomes.
Citation - WoS: 1
Citation - Scopus: 1
Shallow Trapping Centers in Bi12geo20 Single Crystals by Thermally Stimulated Current Measurements
(Elsevier, 2022) Delice, S.; Isik, M.; Gasanly, N. M.
Bi12GeO20 single crystals were investigated by thermally stimulated current (TSC) experiments performed in the temperature range of 10-290 K. Recorded TSC glow curve exhibited six distinctive peaks with maxima at around 90, 105, 166, 209, 246, 275 K. The analyses of the obtained glow curve were accomplished by curve fitting and initial rise methods. The analysis results were in good agreement that the TSC peaks appeared in the glow curve due to existence of trapping levels with activation energies of 0.10, 0.18, 0.23, 0.53, 0.68 and 0.73 eV. These trapping levels were estimated to be hole traps above valence band. The heating rate dependent TSC glow curves were also obtained for various rates between 0.30 and 0.45 K/s. The changes of TSC intensity, peak maximum temperature and full-widths-half-maximum values with heating rates were studied in detail. TSC intensity decreased and peak maximum temperature increased with increasing heating rate. Determination of defects and trapping/stimulation mechanism of those are significant for technological applications since local states in these materials take critical role for device performance.
Citation - WoS: 3
EFFECT OF Y, Au AND YAu NANOSANDWICHING ON THE STRUCTURAL, OPTICAL AND DIELECTRIC PROPERTIES OF ZnSe THIN FILMS
(Natl inst R&d Materials Physics, 2019) Qasrawi, A. F.; Taleb, M. F.
In this article, we report the effects of insertion of yttrium, gold and yttrium-gold (YAu) metallic nano-slabs on the structural, optical and dielectric properties of ZnSe thin films. The ZnSe thin films which are prepared by the thermal evaporation technique under vacuum pressure of 10-5 mbar exhibit hexagonal structure. While the insertion of the 70 nm thick Y layers does not alter the lattice parameters and stress values, the Au and YAu layers increased the lattice parameters along the a- and c-axes and decreased the stress values. In addition, the insertion of these metallic layers slightly alters the value of the energy band gap and increases the width of the interbands. The light absorbability are increased by 1.4, 2.0 and 2.4 times upon insertion of Y, Au and YAu, slabs, respectively. On the other hand, the dielectric and optical conductivity analyses has shown that the use of the YAu stacked metal layers increases the real part of the dielectric constant, the optical conductivity, the drift mobility and extended the plasmon frequency range from 35.1 to 254.0 (Omega cm)(-1), from 1098 to 1766 cm(2)/vs and from 0.94-3.11 GHz to 2.13-4.83 GHz, respectively. The insertion of the two stacked metallic layers between two layers of ZnSe makes the ZnSe more appropriated for thin film transistor technology.
Citation - WoS: 2
Citation - Scopus: 2
Trap Distribution in Agin₅s_{8< Single Crystals: Thermoluminescence Study}
(Pergamon-elsevier Science Ltd, 2018) Delice, S.; Işık, Mehmet; Isik, M.; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
Distribution of shallow trap levels in AgIn5S8 crystals has been investigated by thermoluminescence (TL) measurements performed below room temperature (10-300 K). One broad TL peak centered at 33 K was observed as constant heating rate of 0.2 K/s was employed for measurement. The peak shape analysis showed that the TL curve could consist of several individual overlapping TL peaks or existence of quasi-continuous distributed traps. Therefore, TL experiments were repeated for different stopping temperatures (T-stop) between 10 and 34 K with constant heating rate of 0.2 K/s to separate the overlapping TL peaks. The E-t vs T-stop indicated that crystal has quasi-continuously distributed traps having activation energies increasing from 13 to 41 meV. Heating rate effect on trapped charge carriers was also investigated by carrying out the TL. experiments with various heating rates between 0.2 and 0.6 K/s for better comprehension of characteristics of existed trap levels. Analyses indicated that the trap levels exhibited the properties of anomalous heating rate behavior which means the TL intensity and area under the TL peak increase with increasing heating rate.
Citation - WoS: 14
Citation - Scopus: 15
Investigation of the Physical Properties of the Yb Nanosandwiched Cds Films
(Elsevier Science Sa, 2018) Abed, Tamara Y.; Qasrawi, A. F.; Al Garni, S. E.
In this study, the effects of the sandwiching of a 70 nm thick ytterbium film between two layers of CdS on the structural, compositional, optical and electrical properties are investigated. The X-ray diffraction, scanning electron microscopy, energy dispersion X-ray, visible light spectroscopy and impedance spectroscopy techniques are employed to achieve these effects. It was observed that, the nanosandwiching of Yb between two 500 nm thick films of CdS enhances the crystalline nature of the films without altering the lattice parameters. Particularly, the grain size is increased by 25%, the strain, the defect density and the stacking faults are reduced by 31.5%, 43.7% and 25%, respectively. Optically, the Yb nanosandwiching is observed to enhance the visible light absorbability by at least 2.7 times of the whole range and by 8 times at 1.64 eV. The enhancement of the absorbability is associated with shrinking in the band gap and more interband states. In addition, an increase in the real part of the dielectric constant by 54% is observed when Yb was nanosandwiched in the CdS structure. The modeling of the imaginary part allowed exploring the electron-plasmon interaction parameters. A remarkable increase in the drift mobility from 281 to 996 cm2/Vs associated with plasmon frequency enhancement from 0.84 to 1.38 GHz was determined upon Yb nanosandwiching. The effectiveness of this modeling was verified from the impedance spectra in the frequency domain of 0.01-1.80 GHz, which revealed wave trapping property of ideal values of return loss at notch frequency of 1.35 GHz. Furthermore, the electrical resistivity measurements on the studied samples have shown that the presence of Yb reduced the electrical resistivity and shifts the donor level closer to the conduction band of CdS. The studies nominate the nanosandwiched CdS for use in optical and microwave technologies as dual devices. (C) 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 14
Citation - Scopus: 18
Traps distribution in sol-gel synthesized ZnO nanoparticles
(Elsevier, 2019) Delice, S.; Isik, M.; Gasanly, N. M.
The distribution of shallow traps within the sol-gel synthesized ZnO nanoparticles was investigated using thermoluminescence (TL) experiments in the 10-300 K temperature range. TL measurements presented two overlapped peaks around 110 and 155 K. The experimental technique based on radiating the nanoparticles at different temperatures (T-exc.) between 60 and 125 K was carried out to understand the trap distribution characteristics of peaks. It was observed that peak maximum temperature shifted to higher values and activation energy (E-t) increased as irradiating temperature was increased. The E-t vs. T-exc. presented that ZnO nanoparticles have quasi-continuously distributed traps possessing activation energies increasing from 80 to 171 meV. (C) 2019 Elsevier B.V. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 8
Defect Characterization in Bi₁₂geo_{20< Single Crystals by Thermoluminescence}
(Elsevier, 2021) Delice, S.; Isik, M.; Sarigul, N.; Gasanly, N. M.
Bi12GeO20 single crystal grown by Czochralski method was investigated in terms of thermoluminescence (TL) properties. TL experiments were performed for various heating rates between 1 and 6 K/s in the temperature region of 300-675 K. One TL peak with peak maximum temperature of 557 K was observed in the TL spectrum as constant heating rate of 1 K/s was employed. Curve fitting, initial rise and variable heating rate methods were applied to calculate the activation energy of trap level corresponding to this TL peak. Analyses resulted in a presence of one trap center having mean activation energy of 0.78 eV. Heating rate characteristics of revealed trap center was also explored and theoretically well-known behavior that TL intensity decreases and peak maximum temperature increases with heating rates was observed for the trap level. Distribution of trapping levels was studied by thermally cleaning process for different T-stop between 425 and 525 K. Quasi-continuously distributed trapping levels were revealed with mean activation energies ranging from 0.78 to 1.26 eV. Moreover, absorption analysis revealed an optical transition taking place between a defect level and conduction band with an energy difference of 2.51 eV. These results are in good agreement for the presence of intrinsic defects above valence band in Bi12GeO20 crystals.

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