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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18

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Citation - WoS: 3
Citation - Scopus: 3
Cu Doping of Sb2Se3 Thin Films Via Thermal Evaporation: Tailoring Structural and Optical Properties for Enhanced Photovoltaic Performance
(Elsevier, 2025-10) Isik, M.; Surucu, O.; Bektas, T.; Parlak, M.
In this study, Cu-doped Sb2Se3 thin films were successfully grown using the thermal evaporation method, and their structural and optical properties were systematically investigated. Three different samples with thickness of similar to 400 nm were analyzed: undoped, 1 %, and 2 % Cu-doped Sb2Se3. X-ray diffraction (XRD) analysis revealed well-defined peaks, confirming the orthorhombic crystalline nature of the films. Scanning electron microscopy (SEM) images showed a uniform surface morphology without any significant defects. The optical properties were examined through transmission measurements. The band gap energy determined by Tauc analysis decreased from 1.27 to 1.21 eV as the Cu doping increased from 0 % to 2 %, indicating that Cu incorporation modifies the electronic structure of Sb2Se3. Similarly, Urbach energy increased from 0.148 to 0.168 eV depending on Cu content, suggesting a rise in localized states due to increased structural disorder. These findings demonstrate that Cu doping influences the electronic structure and defect states of Sb2Se3, which is crucial for optimizing its performance in photovoltaic and optoelectronic applications.
Citation - WoS: 7
Citation - Scopus: 7
Characterization of Bi12sio20< Single Crystal: Understanding Structural and Thermal Properties
(Springer Heidelberg, 2024-09-17) 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.
Citation - WoS: 14
Citation - Scopus: 18
Unveiling the Application Potential of Pbmo0.75w0.25< Crystal: Linear and Nonlinear Optical Properties Through Ellipsometry
(Elsevier, 2024-12) Isik, M.; Gasanly, N. M.
PbMo0.75W0.25O4 compound is formed by replacing one quarter of the Mo atoms in the PbMoO4 with W atoms and has significant potential for optoelectronic applications. Optical properties of PbMo0.75W0.25O4 single crystal have been systematically investigated using ellipsometry measurements in the spectral range of 2.4-5.4 eV. The linear optical parameters, including refractive index, extinction coefficient, and absorption coefficient, were extracted from the obtained ellipsometry data. By analyzing spectral dependence of these parameters, band gap energy, critical point energy, and single effective oscillator parameters were determined. The refractive index spectrum was analyzed in the below band gap energy region by considering Cauchy and Sellmeier models. Additionally, nonlinear optical values were calculated, providing a comprehensive understanding of the optical properties of the PbMo0.75W0.25O4 single crystal. This study not only contributes to the fundamental understanding of the crystal's optical properties but also has potential implications for applications in optoelectronic devices and photovoltaics.
Citation - WoS: 6
Citation - Scopus: 6
Identification of Shallow Trap Centers in Inse Single Crystals and Investigation of Their Distribution: a Thermally Stimulated Current Spectroscopy
(Elsevier, 2024-10) Isik, M.; Gasanly, N. M.
Identification of trap centers in semiconductors takes great importance for improving the performance of electronic and optoelectronic devices. In the present study, we employed the thermally stimulated current (TSC) method within a temperature range of 10-280 K to explore trap centers in InSe crystal-a material with promising applications in next-generation devices. Our findings revealed the existence of two distinct hole trap centers within the InSe crystal lattice located at 0.06 and 0.14 eV. Through the leveraging the T-stop method, we offered trap distribution parameters of revealed centers. The results obtained from the experimental methodology employed to investigate the distribution of trap centers indicated that one of the peaks extended between 0.06 and 0.13 eV, while the other spanned from 0.14 to 0.31 eV. Notably, our research uncovers a remarkable variation in trap density, spanning one order of magnitude, for every 10 and 88 meV of energy variation. The results of our research present the characteristics of shallow trap centers in InSe, providing important information for the design and optimization of InSe-based optoelectronic devices.
Citation - WoS: 3
Citation - Scopus: 3
Optical Characterization of Nabi(moo4)2< Crystal by Spectroscopic Ellipsometry
(Springer Heidelberg, 2024-08-12) Guler, I.; Isik, M.; Gasanly, N. M.
The compound NaBi(MoO4)(2) has garnered significant interest in optoelectronic fields. This study employs spectroscopic ellipsometry to thoroughly examine the linear and nonlinear optical characteristics of NaBi(MoO4)(2) crystals, offering detailed insights into their optical behavior. Our investigation presents a precise method for discerning the crystal's spectral features, revealing the spectral variations of key optical parameters such as refractive index, extinction coefficient, dielectric function, and absorption coefficient within the 1.2-5.0 eV range. Through analysis, we determined optical attributes including bandgap energy, critical point energy, and single oscillator parameters. Additionally, we explored the nonlinear optical properties of NaBi(MoO4)(2), unveiling potential applications such as optoelectronic devices, frequency conversion, and optical sensors. This study enhances comprehension of optical properties of NaBi(MoO4)(2), underscoring its significance in future optical and electronic advancements.
Citation - WoS: 28
Citation - Scopus: 30
Exploring Temperature-Dependent Bandgap and Urbach Energies in Cdte Thin Films for Optoelectronic Applications
(Elsevier, 2024-10) 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.
Citation - WoS: 19
Citation - Scopus: 19
Temperature-Dependent Band Gap Characteristics of Bi12sio20< Single Crystals
(Amer inst Physics, 2019-12-27) 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 - Scopus: 2
Material and Device Properties of Si-Based Cu0.5ag0.5< Thin-Film Heterojunction Diode
(Springer, 2019-12-09) Gullu, H. H.; Isik, M.; Delice, S.; Parlak, M.; Gasanly, N. M.
Cu0.5Ag0.5InSe2 (CAIS) thin films were deposited on a glass substrate by sequential sputtering of Cu, Ag, and In2Se3-stacked film layers. Structural characterization showed that the deposited CAIS film satisfies nearly the stoichiometric form with uniform and homogeneous surface structure. The single-phase polycrystalline behavior without any secondary-phase formation was observed from the diffraction profile. The optical properties were investigated using temperature-dependent transmission measurements in the wavelength region of 600-1100 nm and in between 10 and 300 K. In the region of interest, the transmission spectra shifted towards the higher wavelengths as a result of an increase in the sample temperature. The analysis of the absorption data based on the transmission spectra resulted in absorption coefficient values of around 10(5) cm(-1) and the presence of direct allowed optical transition. From the Tauc plots, CAIS samples were found to have three distinct direct optical transitions depending on the possible splitting in the valence band. The obtained room temperature uppermost band gap energy value of 1.09 eV was found in the energy limit of ternary analogues (CuInSe2 and AgInSe2), and also in a good agreement with the previous works in the literature. The dependency of the band gap energy on the temperature was analyzed using fundamental relations. In addition, the electrical characteristics of the film layer were discussed in four-contact conductivity measurements, and room temperature conductivity was observed as 0.8 ohm(-1) cm(-1). Additionally, two activation energy values were found in the temperature-dependent conductivity profile. As a diode application, CAIS/Si heterojunction was fabricated and the main diode parameters were extracted at dark and room temperature conditions.
Citation - WoS: 14
Citation - Scopus: 18
Traps distribution in sol-gel synthesized ZnO nanoparticles
(Elsevier, 2019-06) 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.
Citation - WoS: 14
Citation - Scopus: 15
Structural and Optical Properties of Ga2se3< Crystals by Spectroscopic Ellipsometry
(Springer, 2019-02-06) Guler, I.; Isik, M.; Gasanly, N. M.; Gasanova, L. G.; Babayeva, R. F.
Optical and crystalline structure properties of Ga2Se3 crystals were analyzed utilizing ellipsometry and x-ray diffraction (XRD) experiments, respectively. Components of the complex dielectric function (epsilon=epsilon(1)+i epsilon(2)) and refractive index (N=n+ik) of Ga2Se3 crystals were spectrally plotted from ellipsometric measurements conducted from 1.2eV to 6.2eV at 300K. From the analyses of second-energy derivatives of epsilon(1) and epsilon(2), interband transition energies (critical points) were determined. Absorption coefficient-photon energy dependency allowed us to achieve a band gap energy of 2.02eV. Wemple and DiDomenico single effective oscillator and Spitzer-Fan models were accomplished and various optical parameters of the crystal were reported in the present work.

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