Işık, Mehmet

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https://hdl.handle.net/20.500.14411/8160
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Mehmet, Işık
M.,Işık
Isik, Mehmet
Mehmet, Isik
I., Mehmet
I.,Mehmet
Işık,M.
Isik,M.
I.,Mehmet
M.,Isik
Işık, Mehmet
M., Isik
Isik, M.
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Profesör Doktor
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mehmet.isik@atilim.edu.tr
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Department of Electrical & Electronics Engineering
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Former Staff
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Scholarly Output

173

Articles

169

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Optical Materials17
Physica B: Condensed Matter16
Journal of Luminescence15
Materials Science in Semiconductor Processing14
Journal of Materials Science: Materials in Electronics12
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Subject: Defects

Scholarly Output Search Results

Now showing 1 - 10 of 28
  • Thumbnail Image
    Article
    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.
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    Article
    Citation - WoS: 8
    Citation - Scopus: 8
    Defect Characterization in Bi12geo20< 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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    Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Thermoluminescence characteristics of GaSe and Ga2Se3 single crystals
    (Elsevier, 2022) Isik, M.; Sarigul, N.; Gasanly, N. M.
    GaSe and Ga2Se3 are semiconducting compounds formed from same constituent elements. These compounds have been attractive due to their optoelectronic and photovoltaic applications. Defects take remarkable attention since they affect quality of semiconductor devices. In the present paper, deep defect centers in GaSe and Ga2Se3 single crystals grown by Bridgman method were reported from the analyses of thermoluminescence measurements performed in the 350-675 K range. Experimental TL curves of GaSe and Ga2Se3 single crystals presented one and two overlapped peaks, respectively. The applied curve fitting and initial rise techniques were in good agreement about trap activation energies of 0.83 eV for GaSe, 0.96 and 1.24 eV for Ga2Se3 crystals. Crystalline structural properties of the grown single crystals were also investigated by x-ray diffraction measurements. The peaks observed in XRD patterns of the GaSe and Ga2Se3 crystals were well-consistent with hexagonal and zinc blende structures, respectively.
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    Article
    Citation - WoS: 10
    Citation - Scopus: 11
    Low Temperature Thermoluminescence of Gd2o3< Nanoparticles Using Various Heating Rate and tmax< - texc< Methods
    (Elsevier, 2019) Delice, Serdar; Isik, Mehmet; Gasanly, Nizami M.
    Thermoluminescence (FL) measurements for Gd2O3 nanoparticles were carried out for various heating rates between 0.3 and 0.8 K/s at low temperatures (10-280 K). TL spectrum exhibited two observable and one faint peaks in the temperature region of 10-100 K, and four peaks in the temperature region of 160-280 K. Heating rate analysis was achieved to understand the behaviors of trap levels. It was seen that the peak maximum temperatures and TL intensities of all peaks increase with increasing heating rate. This behavior was ascribed to anomalous heating rate effect. T-max - T(exc )analysis was accomplished for TL, peaks at relatively higher temperature region to reveal the related traps depths. T-max - T-exc plot presented a staircase structure indicating that the TL glow curve is composed of well separated glow peaks. Mean activation energies of trapping centers corresponding to these separated peaks were found as 0.43, 0.50, 0.58 and 0.80 eV.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Trapping Centers in Bi12tio20< Single Crystals by Thermally Stimulated Current
    (Elsevier, 2021) Isik, M.; Delice, S.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.
    Sillenite group compounds have been widely utilized in photocatalytic applications. One of the member of this group, Bi12TiO20 single crystal, was grown by Czochralski method. The structural properties were investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. XRD pattern presented well-defined intensive peaks associated with cubic crystalline structure. SEM images indicated the crystal surface as almost uniform and smooth. Thermally stimulated current (TSC) experiments were performed in the 10-280 K temperature range to reveal shallow trapping centers in the Bi12TiO20 single crystal. Two peaks around 112 and 179 K were observed in the TSC glow curve. The analyses of these curves considering the curve fitting and peak shape techniques resulted in presence of two hole centers at 0.09 and 0.14 eV. Heating rate dependencies of peak maximum temperature and current were also investigated throughout the paper.
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    Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Analysis of Glow Curve of Gas0.5se0.5< Single Crystals
    (Elsevier Science Bv, 2015) Isik, Mehmet; Delice, Serdar; Gasanly, Nizami
    Characterization of shallow trapping centers in GaS0.5Se0.5 crystals grown by a Bridgman method was carried out in the present work using thermoluminescence (TL) measurements performed in the low temperature range of 10-300 K. The activation energies of the trapping centers were obtained under the light of results of various analysis methods. The presence of three trapping centers located at 6, 30 and 72 meV was revealed. The analysis of the experimental glow curve gave reasonable results under the model that assumes slow retrapping which states the order of kinetics as b=1. Heating rate dependence of the observed TL peaks was studied for the rates between 0.4 and 1.0 K/s. Distribution of the traps was also investigated using an experimental technique based on the thermal cleaning of centers giving emission at lower temperatures. The distributed levels with activation energies increasing from 6 to 136 meV were revealed by increasing the stopping temperature from 10 to 52 K. (C) 2015 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 9
    Citation - Scopus: 9
    Thermally Stimulated Current Measurements in Undoped Ga3inse4< Single Crystals
    (Pergamon-elsevier Science Ltd, 2011) Isik, M.; Işık, Mehmet; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
    The trap levels in nominally undoped Ga3InSe4 crystals were investigated in the temperature range of 10-300 K using the thermally stimulated currents technique. The study of trap levels was accomplished by the measurements of current flowing along the c-axis of the crystal. During the experiments we utilized a constant heating rate of 0.8 K/s. Experimental evidence is found for one hole trapping center in the crystal with activation energy of 62 meV. The analysis of the experimental TSC curve gave reasonable results under the model that assumes slow retrapping. The capture cross-section of the trap was determined as 1.0 x 10(-25) cm(2) with concentration of 1.4 x 10(17) cm(-3). (C) 2011 Elsevier Ltd. All rights reserved.
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    Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Low-Temperature Thermoluminescence in Layered Structured Ga0.75in0.25< Single Crystals
    (Elsevier Science Sa, 2012) Isik, M.; Bulur, E.; Gasanly, N. M.
    Defect centers in Ga0.75In0.25Se single crystals have been studied performing the thermoluminescence measurements in the temperature range of 10-300 K. The observed glow curves were analyzed using curve fitting, initial rise, and different heating rate methods to determine the activation energies of the defect centers. Thermal cleaning process has been applied to decompose the overlapped curves. Four defect centers with activation energies of 9, 45,54 and 60 meV have been found as a result of the analysis. The capture cross sections and attempt-to-escape frequencies of the defect centers were also found using the curve fitting method under the light of theoretical predictions. The first order kinetics for the observed glow curve was revealed from the consistency between the theoretical predictions for slow retrapping and experimental results. Another indication of negligible retrapping was the independency of peak position from concentration of carriers trapped in defect levels. (C) 2012 Elsevier B.V. All rights reserved.
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    Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Determination of Trapping Parameters of Thermoluminescent Glow Peaks of Semiconducting Tl2ga2< Crystals
    (Pergamon-elsevier Science Ltd, 2015) Isik, M.; Yildirim, T.; Gasanly, N. M.
    Thermoluminescence (TL) properties of Tl2Ga2S3Se layered single crystals were researched in the temperature range of 290-770 K. U glow curve exhibited two peaks with maximum temperatures of similar to 373 and 478 K. Curve fitting, initial rise and peak shape methods were used to determine the activation energies of the trapping centers associated with these peaks. Applied methods were in good agreement with the energies of 780 and 950 meV. Capture cross sections and attempt-to-escape frequencies of the trapping centers were reported. An energy level diagram showing transitions in the band gap of the crystal was plotted under the light of the results of the present work and previously reported papers on photoluminescence, thermoluminescence and thermally stimulated current measurements carried out below room temperature. (C) 2015 Elsevier Ltd. All rights reserved.
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    Article
    Citation - WoS: 11
    Citation - Scopus: 12
    The Defect State of Yb-Doped Zno Nanoparticles Using Thermoluminescence Study
    (Elsevier Sci Ltd, 2019) Isik, M.; Gasanly, N. M.
    Shallow trapping centers in Yb-doped ZnO nanoparticles were determined using thermoluminescence (TL) measurements applied in the 10-300 K temperature region. Undoped and Yb-doped ZnO nanoparticles were synthesized by sol-gel method. TL glow curve of undoped nano-particles presented three peaks around 56, 108 and 150 K whereas one additional peak around 83 K was observed in the TL curve of Yb-doped ZnO nano-particles. The increase of Yb concentration in the nanoparticles increased the TL intensity of this additional peak. Activation energies of interstitial defect centers were found as 20, 82 and 105 meV while energy of trapping center existing due to Yb-doping was obtained as 72 meV using curve fitting and initial rise methods.