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Citation - WoS: 19
Citation - Scopus: 19
Temperature-Dependent Band Gap Characteristics of Bi₁₂sio_{20< 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.
Citation - WoS: 1
Citation - Scopus: 3
Optical constants and critical point energies of (AgInSe₂)_0.75-(In₂Se₃)_0.25 single crystals
(Springer, 2020) Isik, M.; Nasser, H.; Guseinov, A.; Gasanly, N. M.
AgInSe2 and In2Se3 are two attractive semiconducting materials for various technological applications especially for photovoltaic applications. In the present study, structural and optical properties of (AgInSe2)(x)-(In2Se3)(1-x) crystals for composition of x = 0.75 corresponding to chemical formula of Ag3In5Se9 were characterized by X-ray diffraction, energy-dispersive spectroscopy, room temperature transmission, and ellipsometry experiments. The transmittance spectrum was analyzed to reveal energy band gap. The derivative spectrophotometry analysis resulted in band gap energy of 1.22 eV. The spectra of complex dielectric function, refractive index and extinction coefficient were presented between 1.6 and 6.2 eV from the outcomes of ellipsometry analyses. Critical point energies have been determined using the derivative analyses of dielectric function. Five critical points at 2.70, 3.30, 4.05, 4.73, and 5.42 eV were revealed from the analyses. Crystal structure and atomic composition in semiconducting compound were also reported in the present work. The obtained results were compared with those reported for constituent compounds.
Citation - WoS: 4
Citation - Scopus: 4
TL and OSL studies on gallium sulfide (GaS) single crystals
(Elsevier, 2020) Isik, M.; Yuksel, M.; Topaksu, M.; Gasanly, N. M.
[No Abstract Available]
Citation - WoS: 15
Citation - Scopus: 15
Deep 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.
Citation - WoS: 14
Citation - Scopus: 15
Thermoluminescence Characteristics of Bi 12 Sio 20 Single Crystals
(Elsevier, 2020) Isik, M.; Sarigul, N.; Gasanly, N. M.
[No Abstract Available]
Citation - WoS: 6
Citation - Scopus: 6
Low-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.
Citation - WoS: 4
Citation - Scopus: 4
Optical Characterization of (tlins₂)_{0.5< Crystal by Ellipsometry: Linear and Optical Constants for Optoelectronic Devices}
(Springer, 2023) Guler, I.; Isik, M.; Gasanly, N.
TlInSSe [(TlInS2)(0.5)(TlInSe2)(0.5)] crystals have garnered significant attention as promising candidates for optoelectronic applications due to their exceptional optoelectrical characteristics. This study focused on investigating the linear and nonlinear optical properties of TlInSSe layered single crystals through ellipsometry measurements. The X-ray diffraction analysis revealed the presence of four distinct peaks corresponding to a monoclinic crystalline structure. In-depth analysis was conducted to examine the variations of refractive index, extinction coefficient, and complex dielectric function within the energy range of 1.25-6.15 eV. By employing derivative analysis of the absorption coefficient and utilizing the Tauc relation, the indirect and direct bandgap energies of TlInSSe crystals were determined to be 2.09 and 2.26 eV, respectively. Furthermore, this research paper presents findings on oscillator energy, dispersion energy, Urbach energy, zero and high frequency dielectric constants, plasma frequency, carrier density to effective mass ratio, nonlinear refractive index, and first-order and third-order nonlinear susceptibilities of TlInSSe crystals.
Citation - WoS: 8
Citation - Scopus: 8
Spectroscopic ellipsometry study of Bi₁₂TiO₂₀ single crystals
(Springer, 2021) Isik, M.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.
Bi12XO20 (X: Si, Ge, Ti, etc.) ternary compounds have attracted attention especially due to their fascinating photorefractive characteristics. The present paper introduces the structural and optical characteristics of Bi12TiO20 single crystals grown by Czochralski method. X-ray diffraction pattern of the compound exhibited sharp and intensive peaks corresponding to parallel planes of cubic crystalline structure. The lattice constant of the cubic structure was determined as a = 1.0118 nm using a diffraction pattern indexing program. The optical characterization of the Bi12TiO20 single crystals was carried through spectroscopic ellipsometry experiments performed in the 1.2-5.0 eV spectral range. The spectral dependencies of refractive index, extinction coefficient, and complex dielectric function were revealed analyzing experimental ellipsometric data under the light of sample-air optical model. The band gap energy of the compound was determined as 3.34 eV from the analyses of absorption coefficient. Three critical points at 3.51, 4.10, and 4.71 eV were obtained from the analyses of components of dielectric function using their second-energy derivative spectra.
Citation - WoS: 15
Citation - Scopus: 16
Investigation of Band Gap Energy Versus Temperature for Sns 2 Thin Films Grown by Rf-Magnetron Sputtering
(Elsevier, 2020) Isik, M.; Gullu, H. H.; Terlemezoglu, M.; Surucu, O. Bayrakli; Parlak, M.; Gasanly, N. M.
[No Abstract Available]
Citation - WoS: 5
Citation - Scopus: 5
Revealing 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.

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