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Article Citation - WoS: 14Citation - Scopus: 18Traps 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.Article Citation - WoS: 4Citation - Scopus: 5Thermoluminescence Properties of Tl2ga2< Layered Single Crystals(Amer inst Physics, 2013) Delice, S.; Isik, M.; Bulur, E.; Gasanly, N. M.The trap center(s) in Tl2Ga2S3Se single crystals has been investigated from thermoluminescence (TL) measurements in the temperature range of 10-300 K. Curve fitting, initial rise, and peak shape methods were applied to observed TL glow curve to evaluate the activation energy, capture cross section, and attempt-to-escape frequency of the trap center. One trapping center has been revealed with activation energy of 16 meV. Moreover, the characteristics of trap distribution have been studied using an experimental technique based on different illumination temperature. An increase of activation energy from 16 to 58 meV was revealed for the applied illumination temperature range of 10-25K. (C) 2013 AIP Publishing LLC.Article Citation - WoS: 17Citation - Scopus: 17Trap Distribution in Tlins2 Layered Crystals From Thermally Stimulated Current Measurements(Korean Physical Soc, 2008) Isik, M.; Goksen, K.; Gasanly, N. M.; Ozkan, H.We have carried out thermally stimulated current (TSC) measurements with the current flowing along the layer on as-grown TlInS2 layered single crystals in the low temperature range 10 - 110 K with different heating rates of 0.1 - 1.5 K/s. Experimental evidence was found for the presence of two shallow electron trapping centers with activation energies of 12 and 14 meV. Their capture cross sections have been determined as 2.2 x 10(-23) and 7.1 x 10(-25) cm(2), respectively. It was concluded that retrapping in these centers is negligible, which was confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumed slow retrapping. An exponential distribution of electron traps was revealed from the analysis of the TSC data obtained at different light excitation temperatures. This experimental technique provided a value of 27 meV/decade for the trap distribution. The parameters of the monoclinic unit cell were determined by studying the X-ray powder diffraction.Article Citation - WoS: 2Citation - Scopus: 2Thermoluminescence Characteristics of Tl4gain3< Layered Single Crystals(Taylor & Francis Ltd, 2014) Delice, S.; Isik, M.; Gasanly, N. M.The properties of trapping centres in - as grown - Tl4GaIn3S8 layered single crystals were investigated in the temperature range of 10-300K using thermoluminescence (TL) measurements. TL curve was analysed to characterize the defects responsible for the observed peaks. Thermal activation energies of the trapping centres were determined using various methods: curve fitting, initial rise and peak shape methods. The results indicated that the peak observed in the low-temperature region composed of many overlapped peaks corresponding to distributed trapping centres in the crystal structure. The apparent thermal energies of the distributed traps were observed to be shifted from similar to 12 to similar to 125meV by increasing the illumination temperature from 10 to 36K. The analysis revealed that the first-order kinetics (slow retrapping) obeys for deeper level located at 292meV.Article Citation - WoS: 19Citation - Scopus: 19Temperature-Dependent Band Gap Characteristics of Bi12sio20< Single Crystals(Amer inst Physics, 2019) Isik, M.; Delice, S.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.Bi12SiO20 single crystals have attracted interest due to their remarkable photorefractive characteristics. Since bandgap and refractive index are related theoretically to each other, it takes much attention to investigate temperature dependency of bandgap energy to understand the behavior of photorefractive crystals. The present study aims at investigating structural and optical characteristics of photorefractive Bi12SiO20 single crystals grown by the Czochralski method. The structural characterization methods indicated that atomic composition ratios of constituent elements were well-matched with the chemical compound Bi12SiO20, and grown crystals have a cubic crystalline structure. Optical properties of crystals were investigated by room temperature Raman spectroscopy and temperature-dependent transmission measurements between 10 and 300 K. The analyses of transmittance spectra by absorption coefficient and derivative spectrophotometry techniques resulted in energy bandgaps decreasing from 2.61 to 2.48 eV and 2.64 to 2.53 eV as temperature was increased from 10 to 300 K. The Varshni model was applied to analyze temperature-bandgap energy dependency.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 Citation - WoS: 25Citation - Scopus: 25Temperature-Tuned Band Gap Properties of Mos2 Thin Films(Elsevier, 2020) Surucu, O.; Isik, M.; Gasanly, N. M.; Terlemezoglu, M.; Parlak, M.MoS2 is one of the fascinating members of transition metal dichalcogenides and has attracted great attention due to its various optoelectronic device applications and its characteristic as two-dimensional material. The present paper reports the structural and temperature tuned optical properties of MoS2 thin films grown by RF magnetron sputtering technique. It was observed that the atomic composition ratio of Mo:S was nearly equal to 1:2 and the deposited thin films have hexagonal crystalline structure exhibiting Raman peaks around 376 and 410 cm(-1). The band gap energies were determined as 1.66 and 1.71 eV at 300 and 10 K, respectively and temperature dependency of band gap energy was analyzed by means of Varshni and O'Donnell-Chen models. (C) 2020 Elsevier B.V. All rights reserved.Article Citation - WoS: 22Citation - Scopus: 22Exploring Temperature-Dependent Bandgap and Urbach Energies in Cdte Thin Films for Optoelectronic Applications(Elsevier, 2024) Surucu, O.; Surucu, G.; Gasanly, N. M.; Parlak, M.; Isik, M.This study examines CdTe thin films deposited via RF magnetron sputtering, focusing on structural and optical properties. X-ray diffraction, Raman spectroscopy, and SEM assessed structural characteristics. Optical properties were analyzed through transmittance measurements from 10 to 300 K. Tauc plots and Varshni modeling revealed a temperature-dependent bandgap, increasing from 1.49 eV at room temperature to 1.57 eV at 10 K. Urbach energy rose from 82.7 to 93.7 meV with temperature. These results are essential for applications where temperature affects CdTe-based device performance.Article Citation - WoS: 5Citation - Scopus: 5Optical Properties of Tlgaxin1-x< Mixed Crystals (0.5 ≤ x ≤ 1) by Spectroscopic Ellipsometry, Transmission, and Reflection(Taylor & Francis Ltd, 2014) Isik, M.; Delice, S.; Gasanly, N. M.The layered semiconducting TlGaxIn1-xSe2-mixed crystals (0.5 <= x <= 1) were studied for the first time by spectroscopic ellipsometry measurements in the 1.2-6.2 eV spectral range at room temperature. The spectral dependence of the components of the complex dielectric function, refractive index, and extinction coefficient were revealed using an optical model. The interband transition energies in the studied samples were found from the analysis of the second-energy derivative spectra of the complex dielectric function. The effect of the isomorphic cation substitution (indium for gallium) on critical point energies in TlGaxIn1-xSe2 crystals was established. Moreover, the absorption edge of TlGaxIn1-xSe2 crystals have been studied through the transmission and reflection measurements in the wavelength range of 500-1100 nm. The analysis of absorption data revealed the presence of both optical indirect and direct transitions. It was found that the energy band gaps decrease with the increase of indium content in the studied crystals.Article Citation - WoS: 4Citation - Scopus: 4Thermally Controlled Band Gap Tuning in Cuo Nano Thin Films for Optoelectronic Applications(indian Assoc Cultivation Science, 2024) Delice, S.; Isik, M.; Gasanly, N. M.Temperature dependency of band gap in CuO nano thin films has been investigated by virtue of transmission experiments at different temperatures. Structural and morphological characterization were achieved using X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Analysis on the XRD diffractogram revealed the presence of monoclinic structure for the CuO. Average crystallite size was determined as 17.8 nm. Absorption characteristics in between 10 and 300 K were presented in the wavelength range of 360-1100 nm. The band gap of the CuO was found to be similar to 2.17 eV at 300 K using Tauc and spectral derivative methods. This value increased to similar to 2.24 eV at 10 K. Both methods showed that the band gap extended with decreasing temperature. Temperature dependency of the band gap was studied using Varshni relation. The band gap at absolute temperature, variation of the band gap with temperature and Debye temperature were calculated as 2.242 +/- 0.002 eV, - 5.4 +/- 0.2 x 10(-4) eV/K and 394 +/- 95 K, respectively.
