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Öğe Electronic and optical properties of CdSe/ZnSe core/shell QDs within centered hydrogenic impurity and their tunability when subjected to an external electric field(2024) Jbeli, A. , Zeiri , N. , Yahyaoui , N. , Baser P. , Said , M.Abstract The electronic and optical properties of CdSe/ZnSe semiconductor core/shell quantum dots with hydrogenic donor impurity were investigated theoretically. The perturbation approach and variational method were used in calculations under Effective Mass Approximation. The considered structure is embedded in a variable polymer matrix. The binding energy (BE), photoionization cross-section, polarizability, and diamagnetic susceptibility of the excited impurity were calculated first according to the core/shell radius ratio and then under a significant external electric field and in the absence of an external electric field. A significant stark shift was observed in the BE relative to the embedded matrix element.Öğe Theoretical modeling of nonlinear optical properties in spheroidal CdTe/ ZnTe core/shell quantum dot embedded in various dielectric matrices(ELSEVIER, 2024) S. H ertilli, ,Yahyaoui , N., Zeiri , N., , Baser , P. , Said, M. , Saadaoui , S.The theoretical investigation of the electronic and nonlinear optical properties in spheroid-shaped CdTe/ZnTe core/shell quantum dots (CSQDs) embedded into two commonly adopted dielectric matrices (PVA, SiO ) is done in the framework of the Effective Mass Approximation (EMA). The discrete intra-band confined energy levels and their matching wave functions were calculated by solving the stationary Schr¨ odinger equation taking into account the Compact Density Matrix (CDM) approach. The effect of the dielectric mismatch between the system and the capped matrix has been studied and discussed. Our numerical results revealed that the third-order 2 nonlinear (TON) optical susceptibility dielectric environment.Öğe Theoretical investigation of optoelectronic properties in PbS/CdS core/shell spherical quantum dots under the effect of the electric field intensity, hydrogenic impurity and geometric parameters(Springer, 2024) Jellouli, E.; Zeiri, N.; Başer, Pınar; Yahyaoui, N.; Ed-Dahmouny, A.; Murshed, Mohammad N.; Said, M.In this paper, we theoretically investigated the combined effects of the external electric field (EF) strength and the geometric parameters on the linear, nonlinear and total dielectric functions as well as the effective dielectric function (DF) coefficients of PbS/CdS spherical core/shell quantum dots (CSQD) in the presence of the hydrogenic impurity located at the center. The subband energy eigenvalues and their corresponding wave functions are obtained by solving the time-independent Schr & ouml;dinger equation and using the variational method (VM) in the framework of the effective mass approximation (EMA). The linear, nonlinear and total DF as well as the effective DF were discussed and evaluated under the influence of EF intensity, geometric parameters, the change of the number of quantum dots (QDs) per unit volume and optical intensity I based on the compact density matrix (CDM) approach. The obtained results show that the height peaks of the linear, nonlinear and Total DF as well as the effective DF coefficients increase and their resonant peak moves towards lower energies as the EF and geometric factors increase in both cases with and without considering the hydrogenic impurity effect. Furthermore, our findings show that the impact of optical intensity and the number of QDs per unit volume does not change the resonance peaks of imaginary parts of DF and effective DF but decreases their magnitudes. As a result, we believe that numerical results will present important developments and provide great contributions in designing new optoelectronic devices related to CSQD hetero-nanostructure.Öğe Incorporation of graphene oxide to metal-free phthalocyanine through hydrogen bonding for optoelectronic applications: An experimental and computational study(WILEY, 2023) Yabaş, Ebru; Şenadım Tüzemen, Ebru; Kaya,Savaş; Maslov, Michael M.; Erden, FuatThis paper focuses on incorporation of graphene oxide (GO) to metal-free phthalocyanine (MPc) through only hydrogen bonding and π-π stacking. Briefly, Pc-GO composites at various concentrations were prepared by selfassembly method. The processing time was kept below 10 min to avoid covalent attachment and we aimed at answering the research question of what will happen if the conjugation is realized only through hydrogen bonding under extremely limited processing times. The as-prepared MPc-GO composites were characterized by Fourier transform infrared (FT-IR), UV-Vis, scanning electron microscope (SEM), and fluorescence analysis. We report that the interaction between MPc and GO could immediately be initiated upon mixing of corresponding solutions. Also, complete conjugation by hydrogen bonding andπ-π stacking could be reached even only in 5 min of sonication time. In addition, it was also determined that the prepared MPc-GO composites are stable at room conditions and during dilution. Finally, the optoelectronic properties of MPc and MPc-GO composites were also investigated experimentally and theoretically. Both experimental and theoretical results suggest that MPc-GO composites exhibit improved optoelectronic properties as compared to MPc, even though the conjugation of GO to MPc was only via hydrogen bonding without covalent attachment.Öğe Combined effects of thermodynamic factors and external fields for nonlinear optical processes of deformed Mathieu quantum dot containing central impurity(05.08.2023) Bahar, Mustafa Kemal; Başer, PınarThe theoretical impact of external parameters such as the hydrostatic pressure, temperature, electric field, magnetic field, as well as the Indium (In) concentration and quantum dot width on the nonlinear optical properties of a Mathieu quantum dot (MQD) with a screw dislocation and a hydrogenic impurity at its center, formed by an InxGa1−xAs/GaAs heterojunction, is presented. The wave equation of the system is solved in cylindrical coordinates using the effective mass approximation and the Runge-Kutta-Fehlberg (RKF) method, taking into account the direction of the screw dislocation and the symmetry of the structure. In addition to the screw dislocation, thermodynamic effects, electric and magnetic fields, In concentration, and the width of the MQD have significant effects on the electronic energy levels, dipole matrix elements, and transition frequencies, resulting in important consequences for the nonlinear optical properties. The effects and alternatives of the relevant parameters on the nonlinear optical properties of the MQD with a screw dislocation are discussed in detail. The optical properties that can be altered by these parameters may also be important for experimental studies in determining the optimality of the structure.Öğe Nonlinear optical specifications of the Mathieu quantum dot with screw dislocation(04.08.2023) Bahar, Mustafa Kemal; Başer, PınarIn this study, the nonlinear optical properties of screw dislocation InxGa1−xAs/GaAs Mathieu quantum dots (MQDs) are theoretically investigated for the first time, focusing on the optical rectification (NOR), second harmonic generation (SHG), and third harmonic generation (THG). In addition to the screw dislocation in the structure, external electric and magnetic fields, as well as the Aharonov–Bohm (AB) flux, are applied to the system. The aim of the study is to interpret how the characteristics of the NOR, SHG, and THG of MQDs change depending on the screw dislocation defect, external fields, AB flux, and structural factors such as indium concentration (In) and quantum dot width. The wave equation of the system is solved using the effective mass approximation and the Runge–Kutta–Fehlberg method in cylindrical coordinates, taking into account the direction of twist and the symmetry of the structure. The influence of all parameters on the nonlinear optical properties of the MQD with screw dislocation and their alternatives are discussed in detail. Furthermore, the optimality of the structure is discussed for a certain amount of screw dislocation, which can be important for experimental applications and device designs.Öğe Photoionization Cross Section for H@Cn Implanted in Nonideal Classical Plasmas(2023) Bahar, Mustafa Kemal; Başer, PınarIn this study, photoionization cross sections of guest hydrogen atom in endohedral fullerene (H@Cn) modeled by the Woods–Saxon confinement potential implanted in the nonideal classical plasma (NICP) under spherical confinement are reported for the first time in the related literature. The relevant wave equation is solved numerically via the tridiagonal matrix method and then the energy levels, bound and continuum wave functions are interpreted. Plasma effect is examined by considering plasma temperature and density and is evaluated in the photoionization process. Since the plasma modifies the discrete and continuum spectra by changing the potential energy of hydrogen atom, it closely affects the overlapping of the wave functions of ground state and continuum state. This effect has a distinct response on photoionization resonances. Using different values of endohedral confinement parameters, which means regarding different types of fullerenes, detailed analysis of energy levels, bound and continuum wave functions, and photoionization cross sections are provided by evaluating confinement width, depth, smoothing effect and distance from the spherical encompassement center. The photoionization process of H@Cn implanted in the NICP (nonideal classical plasma) is highly sensitive to both plasma and endohedral confinement. At this sensitivity, Cooper resonance character is like an encoder for fullerene structure.Öğe The second, third harmonic generations and nonlinear optical rectification of the Mathieu quantum dot with the external electric, magnetic and laser field(16.06.2023) Bahar, Mustafa Kemal; Başer, PınarIn this study, the nonlinear optical properties of the ....Öğe Probe of axion-like particles in vector boson scattering at a muon collider(05.09.2023) Salih Cem İnanWe have examined the sensitivity of the axion-like particles (ALP) couplings to electroweak gauge bosons in the diphoton production at a future muon collider. The collisions at the μ+μ− energies of 3 TeV, 14 TeV, and 100 TeV are addressed. The differential cross sections versus the invariant mass of the final photons and total cross section versus minimal diphoton invariant mass are presented. We have derived the exclusion regions for the ALP-gauge boson coupling. The obtained bounds are much stronger than the current experimental bounds in the ALP mass region 10 GeV to 10 TeV. The partialwave unitarity constraints on the ALP-gauge boson coupling are estimated. We have shown that the unitarity is not violated in the region of the ALP coupling studied in the present paper.Öğe Experimental and theoretical insights on the structural and optical properties of GeOx thin films deposited via RF magnetron sputtering under varying oxygen percentage(ELSEVIER, 2023) Şenadım Tüzemen, E.; Hopoğlu, H.; Sarıtaş, S.; Aydınoğlu, H.S.; Ertuğrul, M.; Maslov, M.M.; Kaya, S.; Ungan F; Gür, E.In this study, GeOx films were produced by radio frequency magnetron sputtering (RFMS) under varying oxygen percentages. The structural and optical properties of films grown have been studied experimentally and theoretical calculations have been presented using density functional theory (DFT). Considering the x-ray diffraction (XRD) analysis, Ge (111) peak was observed in the as-deposited film produced only at 2% oxygen percentage. In order to emerge crystal phases, all the amorphous films were annealed at 900 ◦C under atmospheric conditions. It was found that the intensity of the (101) peak increased as the oxygen percentage increased. At the same time, film grown at 2% oxygen percentage was annealed at different annealing temperatures sequentially at 850, 900, and 950 ◦C. As a result, the polycrystalline properties changed as the annealing temperature increased. It was found that the optical properties of the films grown are strongly dependent on the oxygen percentage. As the oxygen percentage has changed, the energy band gap has increased to the values 2.30, 2.31, 2.58, and 6.28 eV. There are Ge-O-Ge antisymmetric stretching peaks appeared at 861.51 cm 1, 949.94 cm 1 and symmetric stretching of hexagonal peaks at 516.34 cm 1, 546.29 cm 1, 581.95 cm 1. The energy band gap results of the density functional theory (DFT) calculations are in good agreement with the experimental observations.Öğe Effect of substrate temperature on Raman study and optical properties of GeOx/ Si thin films(Springer, 2023) Baghdedi, Dhouha; Hopoğlu, Hicret; Demir İlkay; Altuntaş İsmail; Abdelmoula, Najmeddine; ŞenadımTüzemen, EbruIn this study, GeOx thin films were deposited onto Si substrates using the RF magnetron sputtering method. We looked at how the temperature of the substrate affected the Raman spectra and optical characteristics of GeOx thin films. X-ray diffraction was utilized to examine the crystal structure, and a scanning electron microscope was utilized to measure the thickness. In order to investigate the local structure and bonding characteristics, Raman spectroscopy was used. The refractive index, extinction coefficient, and dielectric parameters were calculated using spectroscopic ellipsometry for the 300–1100 nm spectral region. Refractive index and extinction coefficient spectral patterns were discovered by using a sample-air optical model to analyze the experimental ellipsometric data. Notably, a considerable rise in the refractive index was accompanied by a rise in substrate temperature.Öğe Modeling of temperature?dependent photoluminescence of GaN epilayer by artificial neural network(Springer, 2023) ŞenadımTüzemen, Ebru; Yüksek, Ahmet Gürkan; Demir İlkay; Horoz, Sabit; Altuntaş İsmailArtificial neural networks (ANNs) are a type of machine learning model that are designed to mimic the structure and function of biological neurons. They are particularly well-suited for tasks such as image and speech recognition, natural language processing, and prediction tasks. The success of an ANN in modeling a particular dataset depends on factors such as the size and quality of the dataset, the complexity of the model, and the choice of training algorithms. High representation rate of a system in the data set can improve the performance of the ANN model. The study we described is focused on using artificial neural networks (ANNs) to model temperature-dependent photoluminescence (PL) characterization of GaN epilayers grown on patterned sapphire substrates (PSS) using the metalorganic chemical vapor deposition (MOCVD) technique. The ANN model is trained using temperature and wavelength as input parameters and intensity as the output parameter, with the goal of accurately predicting the PL intensity of the GaN epilayer as a function of temperature and wavelength. The model is trained using a large set of experimental data and then tested using data that was not presented to the model during training. The results of the study suggest that ANN modeling methodology is an effective and accurate way of modeling temperaturedependent PL of GaN epilayers grown on PSS. The results of the study suggest that ANN modeling methodology can be used to accurately predict the temperature-dependent PL of GaN epilayers grown on PSS. This means that it may be possible to reduce the number of required experimental measurements by using the ANN model to predict PL intensity at different temperatures, based on a smaller set of experimental measurements. This could potentially save time and resources, while still obtaining accurate information about the optical behavior of GaN-based materials at different temperatures.Öğe Investigating the optical, electronic, magnetic properties and DFT of NiO films prepared using RF sputtering with various argon pressures(ELSEVIER, 2023) Hopoğlu, Hicret; Kaya, Doğan; Maslov, Mikhail M.; Kaya Savaş; Demir İlkay; Altuntaş İsmail; Ungan, Fatih; Akyol, Mustafa; Ekicibil, Ahmet; ŞenadımTüzemen, EbruIn this study, we investigated the structural, optical, magnetic, and conductive properties of nickel oxide (NiO) films on glass substrates deposited using Radio Frequency (RF) magnetron sputtering with varying Ar gas pressure and thickness. X-ray diffraction and Rietveld refinement analysis confirmed a cubic crystal structure and showed that the lattice parameters and the d(111)-space increased from 4.0559 Å to 4.2712 Å and from 2.3208 Å to 2.4582 Å, respectively, due to increased Ar pressure during deposition. Scanning electron microscopy and atomic force microscopy were used to determine the cross-sectional and surface topology of the NiO films, which exhibited uniform and homogeneous growth with an average spherical size of 54.28 ± 0.33 nm. The optical bandgap values of the films were calculated to be between 3.26 and 3.65 eV, increasing with pressure. Hall measurements confirmed the p-type semiconductor nature of the films with an average sheet carrier density of 1010 cm 2. The films exhibited soft magnetic properties, with a maximum Hc and Ms of 178.5 Oe and 5.82 emu/ cm3 for 246 nm NiO film, respectively. Density functional theory (DFT) calculations confirmed the experimental results for both single to five layers NiO films and bulk NiO formations. The refined energy gap value was found to be 3.2 eV by the DFT calculation. The films produced at room temperature were found to be stable and reproducible, making them suitable as p-type materials for device construction.Öğe Comprehensive growth and characterization study of GeOx/Si(ELSEVIER, 2023) Baghdedi, Dhouha; Hopoğlu, Hicret; Sarıtaş, Sevda; Demir İlkay; Altuntaş İsmail; Abdelmoula, Najmeddine; Gür, Emre; ŞenadımTüzemen, EbruIn this study, the reactive radio frequency magnetron sputtering (RFMS) method under varying thickness was used to deposit GeO x on Si substrate at room temperature. The effect of thickness on the structural and optical properties of high-quality germanium dioxide ( GeO 2 ) thin films have been investigated by experimental. Structural properties were investigated using X-ray diffraction. It has been observed that the peak intensity of (113) reflection is the highest in the spectrum of 240.22 nm thickness and using scanning electron microscope (SEM) to calculate thickness of different samples. Reflection measurement, which is one of its optical properties, was measured with an optical spectrophotometer. It has been ob- served that as the thickness increases, the total reflectance changes. The absorption coefficient was calcu- lated using the diffuse reflection curve. From this point of view, the energy band gap was calculated and it was seen that it varies between 4.1 eV and 4.4 eV. As a result, it was observed that the energy band gap increased as the thickness increased. And using spectroscopic ellipsometry to calculate the thickness of different, refractive index, extinction coefficient, and oscillator parameters. The oscillator energy decrease as the thickness of films increases and the dispersion energy increase with the increase of thickness. It have been observed that the thickness varies between 174.29 nm and 332.16 nm. The refractive index increases as the thickness increases.Öğe Neural network predictions of (n, 2n) reaction cross-sections at 14.6 MeV incident neutron energy(2023/1/1) Serkan AkkoyunIn this study, we have estimated the (n,2n) reaction cross-section for 14.6 MeV incident neutron energy by using the artificial neural network (ANN) method. We have also predicted the reaction cross-sections whose experimental data are not available in the literature. For the construction of the present ANN, available experimental data in the literature has been borrowed. The ANN estimations have been compared with the available experimental data and the results from a theoretical calculation and the two commonly used computer codes. According to the results that the ANN results are in good agreement with the experimental data than the codes and this shows that the method can be a powerful tool for the estimation of cross-section data for the neutron-induced reactions. Considering the predictions of the ANN of the cross-sections whose experimental data are not available in the literature, it is seen that they are in line with the trend of the experimental data, but far from the results given by the theoretical calculations and two computer codes.Öğe Predicting -decay energy with machine learning(2023/3/15) Serkan AkkoyunQ β represents one of the most important factors characterizing unstable nuclei, as it can lead to a better understanding of nuclei behavior and the origin of heavy atoms. Recently, machine learning methods have been shown to be a powerful tool to increase accuracy in the prediction of diverse atomic properties such as energies, atomic charges, and volumes, among others. Nonetheless, these methods are often used as a black box not allowing unraveling insights into the phenomena under analysis. Here, the state-of-the-art precision of the β-decay energy on experimental data is outperformed by means of an ensemble of machine-learning models. The explainability tools implemented to eliminate the black box concern allowed to identify proton and neutron numbers as the most relevant characteristics to predict Q β energies. Furthermore, a physics-informed feature addition improved models' robustness and …Öğe Estimation of fission barrier heights for even–even superheavy nuclei using machine learning approaches(2023/3/21) Serkan AkkoyunWith the fission barrier height information, the survival probabilities of super- heavy nuclei can also be reached. Therefore, it is important to have accurate knowledge of fission barriers, for example, the discovery of super-heavy nuclei in the stability island in the super-heavy nuclei region. In this study, five machine learning techniques, Cubist model, Random Forest, support vector regression, extreme gradient boosting and artificial neural network were used to accurately predict the fission barriers of 330 even–even super-heavy nuclei in the region 140 N 216 with proton numbers between 92 and 120. The obtained results were compared both among themselves and with other theoretical model calculation estimates and experimental results. According to the results obtained, it was concluded that the Cubist model, support vector regression and extreme gradient boosting methods generally gave better results and could be a better tool for estimating fission barrier heights.Öğe Performance of machine learning algorithms on neutron activations for Germanium isotopes(2023/7/1) Serkan AkkoyunIn the studies of nuclear physics, one of the important parameters for nuclear reactions is the reaction cross-section. It can be obtained from experimental data or by different theoretical models. In this study, we implement machine learning (ML) algorithms to the regression analysis of the nuclear cross-section of neutron-induced nuclear reactions of Germanium isotopes. The data for the training of the machine was borrowed from the TENDL-2019 library for the total cross-section data of possible nuclear reactions after the bombardment of the different target materials by neutrons. Three ML models, Artificial Neural Networks (ANN), K-Nearest Neighbors (KNN) and, Support Vector Machines (SVM), were developed to fit nuclear data from the TENDL-2019 database in order to predict neutron induce reaction cross sections. The performance of each algorithm is determined and compared by evaluating the mean square error (MSE) and the correlation coefficient (R2). According to the results obtained, we demonstrate that cross-section information can be obtained safely with ML techniques and the regression curve generated by our models is in good agreement with the evaluated nuclear data library. From our study, ANN and KNN are found to be better compared to SVM algorithm. ML models can enhance classical physics-guided models and play a role in nuclear data analyses. They can be used as an alternative to the estimation of cross-sections for neutron energies of an unknown energy value.Öğe Estimation of the S34 (0) S-factor for 3He (?, ?) 7Be reaction by using distorted wave born approximation and artificial neural network(2023/9/6) Serkan AkkoyunThe astrophysical S-factor and total cross-section of radiative capture reaction are analyzed using the first-order distorted wave born approximation and artificial neural network. To make estimations of S 34 (0) at energies going to zero, we have used an artificial neural network model as a new approximation in this area. First, we obtain distorted wave born approximation results using the Gaussian and Woods-Saxon potentials. After, we evaluate artificial neural network approximation to analyze reaction observables of the system. Our results show that artificial neural network model is a powerful candidate as an extrapolation model for astrophysical energies for estimating of the S-factor observable.Öğe Neutron Single-Particle States in 101Sn by Polynomial Fits and Shell Model Calculations for Light Sn Isotopes(2024/2) Serkan AkkoyunThe neutron single-particle energies (SPEs) in 101Sn are one of the main ingredients needed in nuclear studies in the region around the doubly magic 100Sn nucleus. Due to the lack of experimental data on 101Sn spectrum, the determination of SPEs needed for nuclear structure, reaction, and astrophysics studies is a real challenge. This paper discusses the derivation of the relative SPEs outside the doubly magic 100Sn nucleus using a systematic method. We performed 2nd order polynomial fits for each set of experimental data corresponding to the single-particle states d3/2, h11/2, and s1/2 in light odd tin isotopes. By obtaining the single-particle spectrum of 101Sn, neutron SPEs of the model space orbitals are defined. Shell model calculations for even and odd 102−107Sn isotopes are carried out usin g the new interactions, fit1 and fit2. The energy spectra obtained from fit1 and fit2 are presented in comparison with the available experimental data and the results from the other interactions (well-known interaction sn100pn, pc1 obtained by Hartree–Fock method, and set2 obtained by artificial neural network method). Among them, 2 test confirms that fit1, fit2, and set2 are the best to reproduce the experimental spectra of light tin isotopes.
