Yazar "Gunes, Ibrahim" seçeneğine göre listele

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    Effects of carbon content and plasma power on room temperature photoluminescence characteristics of hydrogenated amorphous silicon carbide thin films deposited by PECVD
    (Elsevier Science Sa, 2017) Gunes, Ibrahim; Sel, Kivanc
    The room temperature photoluminescence characteristics of a-SiCx:H thin films, deposited by plasma enhanced chemical vapor deposition technique with various carbon contents (x), at lower (30 mW/cm(2)) (LP) and higher (90 mW/cm(2)) (HP) power densities, were analyzed. The carbon content of the a-SiCx: H thin films was determined by X-ray photoelectron spectroscopy. The peak energies and the full width half maxima of the PL spectra were compared with the optical energies, determined by ultraviolet-visible transmittance measurements and a linearly correlated increase was observed as a function of x. PL peak energies shifted from 1.99 eV to 2.60 eV for LP and from 1.89 to 2.91 eV for HP films. The PL mechanisms were investigated in the frame of the static disorder model and the stokes shift model. Our analyses indicated that for LP films the stokes shift model and for HP films the static disorder model are the dominant mechanisms of PL; moreover it was determined that both of these independent models have contributions to PL mechanism. Additionally, PL spectra were analyzed by the joint density of tail states (JDOS) PL model. The increase in the PL peak energies and spectrum widths by the increase in the plasma power and carbon content considerably fitted to JDOS PL model, which could exclusively represent the PL mechanism by itself. (C) 2017 Elsevier B.V. All rights reserved.
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    Enhancing ?-SnS thin films and fabrication of p-SnS/n-Si heterostructures through flow rate control in ultrasonic spray pyrolysis for improved photovoltaic performance
    (Springer Heidelberg, 2024) Gunes, Ibrahim
    This study presents findings related to the characterization of cubic SnS (pi-SnS) thin films and p-SnS/n-Si heterojunction structures produced simultaneously using the ultrasonic spray pyrolysis technique. In this context, the impact of different spray solution flow rates on the morphological, structural, optical, and electrical characteristics of the films was examined. Morphological analyses revealed that higher flow rates resulted in films with denser and smoother surfaces, approximately 6 nm in roughness. Additionally, it was observed that both the thickness and the growth rate of the films could be adjusted through the modulation of the flow rate. Structural analyses determined that the crystallite size increased and micro-strain values decreased with increasing flow rates. Optical evaluations indicated a decline in the optical band gap of the thin films from about 1.8 eV to 1.7 eV as the flow rates increased. This trend was consistently observed in the data obtained using the Tauc method and the derivative of transmission with respect to wavelength versus photon energy graphs. Electrical analyses revealed that the resistivity values of the thin films increased from 5.24 x 105 ohm cm to 1.64 x 106 ohm cm with increasing flow rates. Furthermore, I-V analyses of the Au/p-SnS/n-Si/Ag heterojunction structures indicated significant variability in key electrical properties. The saturation currents displayed a broad range, suggesting varying efficiencies in charge carrier collection across different samples. Similarly, the change of ideality factors pointed to differences in charge transport mechanisms, while the shifts in barrier heights indicated changes in junction properties with different fabrication conditions. The results of this study offer valuable perspectives for future research.
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    Fine-tuning SnO2 films: Unleashing their potential through deposition temperature optimization by ultrasonic spray pyrolysis
    (Elsevier Sci Ltd, 2024) Sarica, Emrah; Ozcan, Hakan Bilal; Gunes, Ibrahim; Terlemezoglu, Makbule; Akyuz, Idris
    In this study, the optimization of the deposition temperature, which directly affects the crystallinity, morphology, and electrical conductivity of SnO2 films deposited onto Corning Eagle XG glass substrates using the ultrasonic spray pyrolysis technique, was investigated to tailor their physical properties for various applications. Structural analyses revealed that the films had a tetragonal rutile structure, and while films deposited at lower temperatures exhibited a higher prevalence of (200) oriented planes, yet this decreased with an increase in deposition temperature. Morphological analyses showed that the films consisted of grains with octahedral shapes, and films deposited at lower temperatures were found to be more compact. The films had bandgap energy ranges between 3.96 eV and 4.02 eV. Hall effect measurements revealed that not only the carrier concentration decreased from 4.52 x 10(19) cm(-3) to 0.80 x 10(19) cm(-3), but the mobility also decreased from 23.32 cm(2)/Vs to 12.85 cm(2)/Vs. Among all the films, it was noted that the films deposited at 350 degrees C had the highest figure of merit which is 12.3 x 10(-4) Omega(-1). It can be concluded that the changes underlying these variations are associated with structural and morphological changes depending on the substrate temperature. Also, significant results have been attained in applications where precise control over crystal structure and surface morphology is crucial.
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    Flow rate-dependent properties of SnO2 thin films deposited by ultrasonic spray pyrolysis
    (Elsevier, 2024) Gunes, Ibrahim; Sarica, Emrah; Ozcan, Hakan Bilal; Terlemezoglu, Makbule; Akyuz, Idris
    This study unveils the outcomes of fabricating and characterizing SnO2 thin films through ultrasonic spray pyrolysis. Also, it focuses on the effect of manipulating flow rates on their structural, optical, and electrical characteristics. Structural analysis revealed that the films exhibited a tetragonal rutile structure and (200) crystallographic planes become preferential as the flow rate increases. Crystallite size and lattice strain were calculated using the Debye-Scherrer and Williamson-Hall methods, demonstrating that higher the flow rate resulted in larger crystallite sizes and reduced lattice strain. SEM images showed that all films have uniform and consistent film thickness and grain size enlarged with the solution flow rate as well. The films exhibited high optical transparency (>80%) in the visible spectrum, making them suitable for transparent conductive applications. The band gap of the films decreased gradually with flow rates, and the Urbach energy slightly increased. Hall effect measurements revealed higher flow rates resulted in lower sheet resistance (lowest is 1.32 x 10(2) Omega/sq) and higher carrier mobility (highest is 22.12 cm(2)/V.s), indicating improved electrical properties. These findings offer valuable perspectives for forthcoming researches.
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    Fluorine-doped tin oxide films via ultrasonic spray pyrolysis: Investigation of physical properties post-annealing and their potential for TCO applications
    (Elsevier, 2024) Gunes, Ibrahim; Sarica, Emrah; Bilgin, Vildan; Kucukarslan, Ayse; Ozder, Serhat
    In this study, undoped tin oxide (SnO2) and fluorine (F)-doped SnO2 (FTO) films at various doping levels were deposited on glass substrates using the ultrasonic spray pyrolysis technique, followed by an annealing process applied to the films after deposition. In line with this, the study reveals the significant impact of the fluorine doping level optimization on certain physical properties such as the structural, optical, and electrical characteristics of the obtained films, and presents the consequences of the variation in these physical properties for adaptability in various optoelectronic applications. No diffraction peaks were observed in the X-ray diffraction patterns of the deposited films. After the annealing process, however, films with a polycrystalline form and a rutile tetragonal crystal structure were obtained. It was observed that the crystallization levels were better in films doped with 5 % and 10 % F. The optical band gap values of the films were determined to vary between 3.35 eV and 3.68 eV. Furthermore, it was found that with the increase in F doping level, the resistivity (ranging from 2.1 Omega cm to 43.5 Omega cm) and sheet resistance (ranging from 1.62x10(5) Omega/sq to 35.9x10(5) Omega/sq) values of the films decreased, while the figure of merit values (ranging from 0.12x10(-8) Omega(-1) to 67.1x10(-8) Omega(-1)) increased. Among all FTO films, it was revealed that films doped with 10 % F exhibited the highest optical transmittance, the lowest electrical resistivity, and the highest figure of merit values.
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    Non-stoichiometric effect and disorder in as-prepared Cu2ZnSnS4 films deposited at different temperatures by ultrasonic spray pyrolysis
    (Elsevier Sci Ltd, 2022) Gunes, Ibrahim; Bilgin, Vildan; Sarica, Emrah
    A better understanding of its crystal structure, the formation of possible secondary phases, defects and Cu-Zn disorder effects is needed to improve the photovoltaic device performance of CZTS films. In this direction, the effect of deposition temperature on the structural inhomogeneities, such as secondary phases and Cu-Zn dis-order, etc. as well as opto-electrical properties of CZTS were experimentally examined. For this purpose, a non-stoichiometric spraying solution was prepared and ultrasonically sprayed onto glass substrates at different deposition temperatures (350 degrees C, 400 degrees C, 450 degrees C, and 500 degrees C) to obtain CZTS films. Afterward, the structural, morphological, elemental, optical, and electrical properties of the deposited films were investigated in detail. By Lorentzian deconvolution of Raman spectra, 14 Raman vibrational modes were detected and seven of these were assigned to the secondary phases. Also, the ordered-kesterite phase (337 cm-1) of CZTS was found to crystallize along with the disordered-kesterite phase (329 cm-1) due to the disorder of the cation (Cu-Zn) sublattice. Optical band gaps for CZTS films decreased from 1.89 eV to 1.42 eV with increasing in deposition temperature. It was seen that not only optical band gaps but also Cu-Zn disorder and the amount of secondary phases in CZTS films tightly depend on the deposition temperature.
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    Room temperature photoluminescence spectrum modeling of hydrogenated amorphous silicon carbide thin films by a joint density of tail states approach and its application to plasma deposited hydrogenated amorphous silicon carbide thin films
    (Elsevier Science Sa, 2012) Sel, Kivanc; Gunes, Ibrahim
    Room temperature photoluminescence (PL) spectrum of hydrogenated amorphous silicon carbide (a-SiCx:H) thin films was modeled by a joint density of tail states approach. In the frame of these analyses, the density of tail states was defined in terms of empirical Gaussian functions for conduction and valance bands. The PL spectrum was represented in terms of an integral of joint density of states functions and Fermi distribution function. The analyses were performed for various values of energy band gap, Fermi energy and disorder parameter, which is a parameter that represents the width of the energy band tails. Finally, the model was applied to the measured room temperature PL spectra of a-SiCx:H thin films deposited by plasma enhanced chemical vapor deposition system, with various carbon contents, which were determined by X-ray photoelectron spectroscopy measurements. The energy band gap and disorder parameters of the conduction and valance band tails were determined and compared with the optical energies and Urbach energies, obtained by UV-Visible transmittance measurements. As a result of the analyses, it was observed that the proposed model sufficiently represents the room temperature PL spectra of a-SiCx:H thin films. (C) 2012 Elsevier B.V. All rights reserved.
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    Tailoring the physical properties of ultrasonically spray pyrolyzed SnS thin films with silver doping
    (Springer, 2025) Gunes, Ibrahim; Sarica, Emrah; Bilgin, Vildan; Kucukarslan, Ayse
    In this study, the effects of silver (Ag) doping on the structural, morphological, optical, and electrical properties of tin monosulfide (SnS) thin films were investigated. The films, undoped and doped with 3%, 6%, and 9% Ag, were deposited using the ultrasonic spray pyrolysis (USP) technique at a substrate temperature of 350 degrees C. X-ray diffraction (XRD) analysis confirmed a pi-SnS (cubic) structure with (400) preferred orientation for undoped and <= 6% Ag-doped films, while 9% doping induced amorphization due to severe lattice distortions. Morphological analyses revealed smooth, void-free surfaces, with average roughness increasing from 5.8 nm (undoped) to 19.6 nm (9% doping). Optical measurements showed that the band gap widened from 1.84 eV (undoped) to 2.47 eV (9% Ag-doped), and Urbach energy increased from 190 meV to 600 meV. Hall effect measurements confirmed p-type conductivity for all films. Resistivity ranged from 4.34 x 10(5) Omega cm to 9.48 x 10(5) Omega cm, carrier concentration varied between 2.7 x 10(12) cm(-3) and 5.6 x 10(12) cm(-3), while mobility decreased from 3.3 x 10(1) cm(2)/Vs to 2.0 x 10(1) cm(2)/Vs with increasing Ag doping. These findings demonstrate that Ag doping significantly influences the structural and optoelectronic behavior of SnS thin films, making them promising candidates for thin-film solar cells and optoelectronic applications.
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    The Effect of Fe and Co doping on the Physical Properties of CdO Films Deposited by Ultrasonic Spray Pyrolysis
    (Springer, 2025) Demirselcuk, Barbaros; Gunes, Ibrahim; Sarica, Emrah; Kus, Esra; Kucukarslan, Ayse; Bilgin, Vildan
    In this study, Cadmium Oxide (CdO) semiconductor films with different iron (Fe) and cobalt (Co) concentrations have been produced at 350 degrees C substrate temperature on the glass substrates by the ultrasonic spray pyrolysis method. In the first part of this study, the Fe element was doped in different ratios (2, 4, 6%) to CdO films, and the films were characterized. At the end of this stage, the optimum Fe doping ratio was determined for CdO films. In the second step, CdO films were dually doped with Fe + Co. The electrical resistivities of CdO:Fe films were determined using a four-probe technique to measure their conductivities, carrier concentrations, mobilities, and electrical conductivity types through Hall measurements. The produced films showed n-type electrical conductivity. It was determined that with increasing doping ratios, the electrical resistivity generally increased, and the films exhibited n-type conductivity. The XRD patterns revealed that the crystal structures of the films were polycrystalline and cubic in structure. The lections of (111), (200), (220), (311), and (222) planes were observed in the XRD patterns. Upon examination of the SEM images, it was observed that the films had nearly homogeneous surfaces and good adhesion to the substrate. By utilizing the fundamental absorption spectra of the films, it was determined that they exhibited direct bandgap transitions, and the bandgap energy values ranged from 2.34 to 2.65 eV. In the structural analysis, all films were found to have a polycrystalline structure and cubic CdO crystal system. When the SEM images of CdO:(Fe + Co) films were examined, it was observed that the films had almost homogeneous surfaces. Based on all these analyses, it was concluded that the doping elements Fe and Co significantly influenced the physical properties of CdO thin films.