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Öğe Characterization of Bi12SiO20 single crystal: understanding structural and thermal properties(Springer Heidelberg, 2024) Altuntas, G.; Isik, M.; Gasanly, N. M.This study presents a thorough examination of the structural and thermal characteristics of Bi12SiO20 crystal. X-ray diffraction (XRD) analysis was employed to investigate the crystallographic structure, while scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to ascertain morphological features and elemental composition, respectively. The XRD spectrum exhibited numerous peaks corresponding to the cubic crystalline structure. Thermal behavior was investigated through thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Within the crystal, negligible weight loss was observed up to 750 degrees C, followed by weight loss processes occurring in the temperature ranges of 750-919 degrees C and above 919 degrees C. The 2% weight loss in the range of 750-919 degrees C was associated with the decomposition process, and the activation energy of this process was found to be 199 kJ/mol considering Coats-Redfern expression. A significant weight loss was observed in the region above 919 C-o and was associated with the decomposition of the Bi12SiO20 compound and/or the melting processes of the components of the Bi12SiO20 compound. Three endothermic peaks were observed in the DTA plot. Additionally, DSC measurements conducted under varied heating rates indicated endothermic crystallization process around 348 degrees C, with an activation energy of 522 kJ/mol determined through the Kissenger equation. These findings present valuable details regarding the crystal's structural configuration, morphological attributes, and decomposition/phase transitions, thereby illuminating its potential applications across various fields.Öğe Exploring 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.Öğe NaBi(MoO4)2 crystal: Defect states and luminescence properties for optoelectronic applications(Elsevier, 2025) Isik, M.; Altuntas, G.; Gasanly, N. M.; Darvishov, N. H.This paper investigates the electronic and optical properties of NaBi(MoO4)2 crystal through absorbance, thermally stimulated current (TSC), and photoluminescence (PL) measurements. Absorbance analysis revealed important information about the bandgap and the degree of disorder within the material. The bandgap energy of the compound was found to be 2.94 eV. TSC measurements revealed the presence of hole defect centers and provided information regarding charge transport mechanisms. Two TSC peaks were observed at temperatures of 69.3 and 127.5 K, and the activation energies of the trap centers associated with these peaks were found to be 0.05 and 0.14 eV. Two PL peaks were observed around 487 and 536 nm corresponding to the blue and green emissions, respectively. These findings provide a comprehensive understanding the band structure of the NaBi (MoO4)2, highlighting its suitability for use in optoelectronic devices, sensors, and light-emitting applications.Öğe Spectroscopic ellipsometry study of linear and nonlinear optical properties of NaBi(Mo0.5W0.5O4)2 crystal(Springer, 2024) Isik, M.; Guler, I.; Gasanly, N. M.; Darvishov, N. H.In this study, linear and nonlinear optical characteristics of NaBi(Mo0.5W0.5O4)(2) crystal, a new material that may have potential for optoelectronic applications, were investigated. NaBi(Mo0.5W0.5O4)(2) single crystals were grown via the Czochralski method. Two sharp and well-defined peaks were observed in the x-ray diffraction pattern. These peaks were associated with tetragonal crystal structure. The data obtained from ellipsometer measurements was matched with a suitable optical model. This allowed for the presentation of the spectral dependence of various optical parameters like refractive index, dielectric constant, optical conductivity, extinction, and absorption coefficients in the range of 1.2-5.0 eV. As a result of studying the spectral dependence of the absorption coefficient under Tauc relationship, bandgap energy of the compound was found to be 3.20 eV. Using the spectral dependence of the dielectric function, the existence of two critical points with energy values of 3.72 and 4.44 eV was revealed. The change of the refractive index in the region under the bandgap was studied using the single oscillator model. Single oscillator and dispersion energies were determined from the analysis results. Nonlinear optical parameters of NaBi(Mo0.5W0.5O4)(2) crystal were also determined. With this study, the optical properties of the NaBi(Mo0.5W0.5O4)(2) are presented in more detail and valuable information is presented for the potential use of the material in optoelectronic devices.
