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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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    Phase transition of ultrasonically sprayed VOx thin films: The role of substrate temperature
    (Elsevier Gmbh, 2021) Sarıca, Emrah; Bilgin, Vildan; Akyuz, Idris
    In this study, vanadium oxide (VOx) semiconductor films were deposited on glass substrates using ultrasonic spray pyrolysis technique. The effect of the substrate temperature on the physical properties of the deposited thin films was investigated. For this purpose, 0.05 M VCl3 aqueous solutions were prepared and sprayed on glass substrates at different temperature of 225 degrees C, 275 degrees C, 325 degrees C and 375 degrees C. Structural properties of VOx thin films were investigated by taking xray diffraction (XRD) patterns and it was determined that the films deposited at 225 degrees C and 275 degrees C have tetragonal V4O9 phase while the ones deposited at 325 degrees C and 375 degrees C have mixture of alpha-V2O5 and beta-V2O5, alpha-V2O5 being dominant. The optical band gap energies of the films were determined to be in the range of 2.29 eV to 2.42 eV. Electrical investigations revealed that VOx films have n-type conductivity and electrical resistivity decreased from 4.07 Omega cm to 0.67 Omega cm depending on the increase in substrate temperature. Scanning electron microscopy (SEM) images showed that morphology of the films highly is sensitive to substrate temperature.
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    Sol-gel derived ZnO:Sn thin films and fabrication of n-ZnO:Sn/p-Si heterostructure
    (Elsevier B.V., 2021) Sarıca, Emrah; Gunes, Ibrahim; Akyuz, Idris; Bilgin, Vildan; Erturk, Kadir
    In this work ZnO:Sn thin films were deposited onto glass and p-Si substrates by spin coating of prepared sols which contains different amounts of Zn(CH3COO)2·2H2O and SnCl2 (0, 5, 10 and 15%). Physical properties of ZnO films were examined as a function of SnCl2 in prepared sols. In addition to that, heterostructure examinations were also carried out by depositing all films on p-Si substrates as well. XRD studies revealed that all films have c-axis orientation with crystallite sizes between 38 and 47 nm. AFM and SEM images showed that morphology of the films remarkably deteriorated with the increase in amount of SnCl2 in sol. Optical transmittance and absorbance spectra showed that films have high transmittance and low absorbance in the visible region. Besides, optical band gap increased from 3.27 eV to 3.37 eV. Additional band gap energies were determined for 10% and 15% Sn doped ZnO films. Room temperature photoluminescence spectra for all films were deconvoluted for the evaluation of all emission bands and it was noted that incorporation of SnCl2 into sol led to enhancement of UV-blue emission bands and caused emission bands related to oxygen vacancies to diminish. Four-point-probe measurements revealed that electrical resistivity of ZnO:Sn films increased from 3.20 × 100 Ωcm to 2.82 × 104 Ωcm and diode ideality factor of Ag/ZnO:Sn/p-Si/Au heterostructure was calculated to be in the range of 2.14–4.59 while zero-bias barrier height is in the range of 0.63–0.78 eV.
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    Ultrasonically sprayed cobalt oxide thin films: Enhancing of some physical properties by nickel doping
    (Elsevier B.V., 2021) Kus, Esra; Kucukarslan, Ayse; Demirselcuk, Barbaros; Sarıca, Emrah; Akyuz, Idris; Bilgin, Vildan
    In this study, the effect of Ni doping (3, 6, 9 at%) on structural, optical, electrical and magnetic properties of Co3O4 films was reported. Films were grown at 300 ± 5 °C substrate temperature via ultrasonic spray pyrolysis (USP) technique. The structural analyses showed that undoped and Ni (3%) doped films exhibit an amorphous structure. Ni doping at higher ratios caused the films to have improved crystallinity. Optical band gap values the films were found to be between 2.03 and 2.08 eV with an additional sub-band corresponding to energies varying between 1.35 and 1.46 eV. The electrical conductivity values of the films increased significantly depending on the Ni doping. The hysteresis curves of the films showed that the films have weak ferromagnetic properties. Ni doping significantly improved the structural and electrical properties of Co3O4 films making them suitable materials for technological applications.