Browsing by Author "Gunes, Ibrahim"

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Fine-Tuning Sno2 Films: Unleashing Their Potential Through Deposition Temperature Optimization By Ultrasonic Spray Pyrolysis
(Başkent Üniversitesi Mühendislik Fakültesi, 2024-03-31) 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.
Flow Rate-Dependent Properties Of Sno2 Thin Films Deposited By Ultrasonic Spray Pyrolysis
(Başkent Üniversitesi Mühendislik Fakültesi, 2024-05-02) 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.
Fluorine-Doped Tin Oxide Films Via Ultrasonic Spray Pyrolysis: Investigation Of Physical Properties Post-Annealing And Their Potential For Tco Applications
(MATERIALS TODAY COMMUNICATIONS, 2024-12) 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.
Non-Stoichiometric Effect And Disorder In As-Prepared Cu2ZnSnS4 Films Deposited At Different Temperatures By Ultrasonic Spray Pyrolysis
(2022) Gunes, Ibrahim; Bilgin, Vildan; Sarica, Emrah; https://orcid.org/0000-0002-9339-5114; AAW-6723-2020
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.