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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: 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.Article Low Temperature Thermoluminescence of Quaternary Thallium Sulfide Tl4inga3<(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.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: 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.
