Master Degree / Yüksek Lisans Tezleri

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Now showing 1 - 10 of 46
  • Master Thesis
    Liquid Crystal Templated Synthesis of Metal Oxides and Their Characterization
    (01. Izmir Institute of Technology, 2024) Demir, Seren; Balcı, Fadime Mert
    Sıvı kristaller, katılar ve sıvılar arasında özellikler gösteren fazlar olup malzeme bilimi ve teknolojisinde önemli bir yere sahiptir. Bu malzemeler, moleküllerinin dizilimi ve hareket serbestliği sayesinde hem sıvıların hem de kristallerin özelliklerini birleştirir. Özellikle termotropik ve liyotropik sıvı kristaller, sıcaklık ve çözücü konsantrasyonuna bağlı olarak farklı fazlara geçiş yapabilen yapılar sunar. Sıvı kristallerin sergilediği mezofazlar moleküler dizilimine göre sınıflandırılır. Bu mezofazlar, özellikle optoelektronik uygulamalarda, sensörlerde ve biyomimetik malzemelerde önemli rol oynar. Yüzey aktif maddeler, suyun varlığında çeşitli liyotropik sıvı kristal (LLC) mezofazları oluşturmak üzere organize olurlar. Bu tezde, Sıvı Kristal mezofazları kullanılarak Molibden trioksit filmleri sentezlendi ve bu filmler farklı karakterizasyon teknikleri kullanılarak karakterize edildi. Ayrıca, Sıvı Kristal şablonlu Çinko oksit ince filmler aynı şekilde sentezlendi ve farklı karakterizasyon teknikleri kullanılarak karakterize edildi. Ayrıca, Çinko Oksit filmler için pozitif yüklü CTAB yüzey aktif maddesinin filmler üzerindeki etkisi araştırıldı. Farklı kalınlıklardaki çinko oksit filmlerin Tauc Plot ile bant aralığı hesaplaması yapıldı. Ayrıca, Metal Organik Çerçevelerden biri olan ZIF-8, Çinko oksit ince filmler üzerinde sentezlendi ve karakterize edildi.
  • Master Thesis
    The Effect of Bending Cycles on Optical and Electrical Properties of Multilayer Zto Ag Zto and Ito Transparent Conductive Oxide Thin Films Grown by Magnetron Sputtering
    (01. Izmir Institute of Technology, 2024) Çelikli, Cenkay; Özyüzer, Lütfi; Özdemir, Mehtap
    Bu tez, esnek yüzeylerde büyütülen Çinko Kalay Oksit (ZTO, Zn2SnO4)/Ag/ZTO (ZAZ) ve İndiyum Kalay Oksit (ITO, In2O3:SnO2) ince filmlerin yapısal, elektriksel ve optik özelliklerini incelemektedir. Karşılaştırma, İndiyum elementinin azalan bulunabilirliği ve yüksek maliyetleri nedeniyle yapılmıştır. Bu doğrultuda, gümüş ile tamamlanan ZTO tabanlı bir sandviç yapı geliştirilmiştir; bu yapı, yüksek iletkenlik ve şeffaflık gerektiren Şeffaf İletken Oksit (TCO) uygulamalarında ITO'ya benzer özellikler sunmaktadır. Deneysel çalışmalarda, magnetron sputtering tekniği kullanılarak ince film kaplama için optimum parametreler belirlenmiş ve polikarbonat yüzeyler üzerine örnekler büyütülmüştür. Yapısal karakterizasyon için yapışma testleri, profilometri ve Taramalı Elektron Mikroskobu (SEM) kullanılmış; elektriksel özellikler 2-probe ve 4-probe yöntemleriyle, optik özellikler ise spektrofotometre ile ölçülmüştür. Sonuçlar, ZAZ çok katmanlı yapısının ITO kaplamalarına kıyasla daha iyi performans sergilediğini göstermiştir. Bu çalışma, ZAZ ince filmlerinin ITO yerine kullanılabileceğini ve esnek giyilebilir teknolojilerdeki gelecekteki uygulamaları için bir rehber sunduğunu ortaya koymaktadır.
  • Master Thesis
    Growth and characterization of LiCoO2 thin films by magnetron sputtering for lithium ion batteries
    (01. Izmir Institute of Technology, 2024) Özcan, Polatkan; Özyüzer, Gülnur Aygün
    Bu tez, lityum iyon pillerde kullanılmak üzere mıknatıssal saçtırma yöntemiyle büyütülen ve karakterize edilen Lityum Kobalt Oksit (LiCoO₂) ince filmlerinin geliştirilmesi ve iyileştirilmesine odaklanmaktadır. Yüksek performanslı enerji depolama cihazlarına yönelik artan talep göz önünde bulundurularak, bu çalışmada LCO ince filmlerin elektrokimyasal özelliklerini iyileştirmek için kaplama parametrelerinin optimize edilmesine gayret edilmektedir. İleri karakterizasyon teknikleri, örneğin Taramalı Elektron Mikroskobu (SEM), Enerji Dağılımlı X-ışını Spektroskopisi (EDX), X-ışını Difraksiyonu (XRD), Raman Spektroskopisi, X-ışını Fotoelektron Spektroskopisi (XPS) ve Elektrokimyasal Döngüsel Voltametri filmlerin morfolojisini, bileşimini, kristal yapısını ve kimyasal durumlarını değerlendirmek için kullanılmaktadır. Ayrıca, bu araştırma tüm katı hal lityum iyon pillerde (ASSLIB'ler) elektrolit/katot ara yüzeyindeki zorluklara değinmekte olup, ara yüzey kararlılığını artırmayı ve direnci azaltmayı hedeflemektedir. Kaplama sürecinin iyileştirilmesi ve ara yüzey özelliklerinin kapsamlı bir şekilde anlaşılması ile çalışma, lityum iyon pillerin genel performansını ve güvenliğini önemli ölçüde artırmayı amaçlamaktadır. Bu araştırmadan elde edilen bulgular, pil teknolojisinin ilerlemesine katkıda bulunarak, daha verimli ve kararlı enerji depolama çözümlerinin geliştirilmesi için değerli içgörüler sunmaktadır. Bu çalışma, malzeme optimizasyonunun önemini vurgulamakta ve çeşitli uygulamalarda daha iyi performans, uzun ömür ve güvenlik sağlamak için pil teknolojisinde gelecekteki yenilikler için bir yol sunmaktadır.
  • Master Thesis
    Electrical Characterization of Vanadium Dioxide (vo₂) Thin Films Grown by Magnetron Sputtering Technique
    (01. Izmir Institute of Technology, 2024) Akyürek, Bora; Özyüzer, Gülnur Aygün
    The aim of this thesis is to determine the parameters required for the production of pure VO₂ thin films and to evaluate the usability of these films by calculating their MIT ratios. Vanadium dioxide (VO₂), a substance that exhibits a phase transition from the insulating state to the metallic state at approximately 68 °C, shows significant changes in its electrical conductivity and optical properties. To get pure VO2 thin films, and get optimum parameters for deposition, several parameters were varied during the manufacturing process,including temperature, oxygen-argon ratio, and coating time. Then, electrical characterization of the produced films was performed. Examining the temperature dependence of the resistance of thin films has been a critical aspect of electrical measurements to determine the MIT transition. With the help of the probe station, it was determined that the MIT transition occurred at approximately 68 °C. The results obtained using structural characterization techniques revealed that characteristic vibration modes were observed in the analyses performed with Raman spectroscopy, while XRD analyses revealed that the crystal structure was preserved. Additionally, XPS analyses did not detect any surface contamination other than carbon. SEM and EDX analyses evaluated the surface morphology and elemental stoichiometry and showed that the internal structure of the films was intact. These results support the usability of VO₂ thin films in advanced electronic and optical applications and contribute to the determination of optimum production parameters. This thesis demonstrates the potential of VO₂ in various technological applications by efficiently utilizing MIT properties.
  • Master Thesis
    Lyotropic Liquid Crystal Templated Synthesis of Single-Crystalline Gold Microplates and Transparent Conductive Reduced Graphene Oxide Thin Films
    (01. Izmir Institute of Technology, 2023) Akkuş, Betül; Mert Balcı, Fadime
    Surfactants organize to form various mesophases of lyotropic liquid crystal (LLC) in the presence of water. In the literature, some acids, salts, and ionic liquids have also been used to form ordered LLC mesophases. In this thesis, two dimensional (2D) single-crystalline gold (Au) nano- and microplates and reduced graphene oxide (RGO) thin films have been synthesized using LLC mesophases. Stable LLC mesophases have been formed using 10-lauryl ether (C12EO10), an oligo-type surfactant, and sulfuric acid (H2SO4), a strong acid. Au plates with various anisotropic structures, such as triangular, truncated triangular, hexagonal, and gear-like, have been synthesized by a photochemical method in the presence of LLC mesophase. Most importantly, Au plates up to 39 µm in width have been obtained in the confined space of the LLC medium. The thickness of the obtained Au plates varies from 50 nm to 150 nm. The size and/or morphology of Au products synthesized in LLC medium depends on the power of the light source, the irradiation time, the amount of Au precursor added, the addition of different capping agents, and various inorganic salts. Additionally, spin-coated RGO thin films have been synthesized using the LLC mesophase for use as a transparent and conductive electrode in various electrochemical devices. The LLC mesophase has improved the sheet resistance values of RGO thin films. RGO thin films with a sheet resistance of 31 kΩ/sq and an optical transmittance of 92% at 550 nm have been achieved at the high thermal annealing temperature under an inert atmosphere.
  • Master Thesis
    Sb2se3 Absorber Layered Solar Cell Fabrication and Characterization
    (01. Izmir Institute of Technology, 2021) Kurtuldu, Seher Hazal; Aygün Özyüzer, Gülnur; Tarhan, Enver
    Thin-film antimony selenide (Sb2Se3) solar cells have gained attention as a high-potential photovoltaic technology around the world. Outstanding features like a high absorption coefficient, a suitable direct bandgap, and good hole mobility make Sb2Se3 a promising absorber material for solar cell applications. It has demonstrated a very rapid growth reaching 9.2% power conversion efficiency (PCE) in only 7 years after intensive studies. In the present thesis, first of all Sb2Se3 thin films were deposited on soda lime glasses (SLGs) and investigated using energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM), spectrophotometry and Raman spectroscopy. Structural and optical studies were carried out depending on the thickness, used argon (Ar) gas flow rate and post-annealing temperature of the Sb2Se3 films in order to optimize the absorber layer to be used in solar cell. This study revealed that key parameters such as band gap energy and crystal structure of the Sb2Se3 thin films affected by the thickness, Ar gas flow rate during deposition and post-annealing temperature. In addition, oxide phase formation was also found to be related to these growth parameters. Finally, SLG/ITO/Zn(O,S)/Sb2Se3/Ag for superstrate configuration and both SLG/Mo/Sb2Se3/CdS/ITO and SLG/Mo/Sb2Se3/CdS/ZnS/ITO devices fabricated for substrate configuration solar cells. Since Zn(O,S)/Sb2Se3 heterojunction has not been studied before in the literature, this study will be the first. At the end of the electrical analysis, the best conversion efficiency of 3.9% was achieved by the solar cell with the substrate configuration.
  • Master Thesis
    Development of Conductive Oxide Based Thin Film Modified Electrodes and Biosensors Applications
    (Izmir Institute of Technology, 2021) Yurttaş, Betül; Özyüzer, Lütfi; Erdem Gürsan, Kadriye Arzum
    From the first biosensor produced in 1956 to the present day, biosensors have been highly developed and diversified. In biosensor manufacturing, thin films have become a rapidly emerging field. Depending on the thin film material used, thin films have many advantageous properties for biosensors, such as high surface-to-volume ratio, conductivity, stability, specificity, biocompatibility, and good electrocatalytic activity. Dopamine is a neurotransmitter that has a significant impact on the emergence and treatment of certain diseases such as Alzheimer's and Parkinson's diseases. Dopamine monitoring is important for the prevention of these diseases, and it is a favorable option to use biosensors, which are useful and practical tools, instead of time-consuming and expensive conventional methods. For this purpose, in this thesis, a non-enzymatic electrochemical biosensor based on thin film electrodes was developed for monitoring dopamine levels. The electrodes were developed by deposition of Zn2SnO4 (ZTO) thin film on ITO thin film substrate by DC magnetron sputtering technique. The properties of the electrodes were determined by thickness, optical transmittance, XRD and SEM analysis. Electrochemical analysis, namely CV, EIS and DPV measurements, were performed before and after the electrodes were sonicated and modified with APTES before their application to the voltammetric detection of dopamine. In addition, electrochemical measurements were performed before/after sonication, APTES modification. Dopamine was detected by a voltammetric method using DPV technique. Furthermore, experiments in the presence of interferents such as ascorbic acid (AA), uric acid (UA) etc. showed that the thin film electrodes can be successfully applied for voltammetric determination of dopamine. As a result, the biosensor technology developed in this study has the potential to be wearable in the future, enabling non-invasive monitoring of dopamine levels in body fluids such as saliva, tears and sweat.
  • Master Thesis
    The Growth of Vanadium Dioxide Thin Films by Magnetron Sputtering Technique and Terahertz Wave Modulation Characteristics
    (01. Izmir Institute of Technology, 2020) Ata, Bengü; Özyüzer, Lütfi
    Vanadium dioxide (VO2) is a fascinating material thanks to its unique insulator-metal transition (IMT) at 68 °C which is very close to the room temperature. This reversible change in electrical resistivity is around several orders of magnitude and the electrical change accompanied by optical and structural change as well. Thanks to these unique properties vanadium dioxide material has been studied intensively past decades. This phase transition allows us to apply the transition properties widen application such as field effect transistor (FET), uncooled bolometers, tunable metamaterial filters, high data rate wireless communication etc. Especially for terahertz region which is the most unexplored region of the electromagnetic spectrum, vanadium dioxide is a promising material having ability to modulate terahertz waves by IMT phenomena. In this work, vanadium dioxide (VO2) thin films fabricated by reactive DC magnetron sputtering method and its properties optimized to minimize the amounts of secondary phases by optimizing the oxygen concentration, sputtering power and deposition time. Samples which show the maximum resistivity change during the transition have been used for the terahertz modulation experiments. It has been observed that when the VO2 samples triggered by continuous wave (CW) laser, VO2 transforms to the metallic phase, behave as an opaque material to the terahertz wave. At room temperature, in insulating phase it is partially transparent to terahertz radiation. This results indicate that VO2 thin films can be a good candidate for THz wave modulators.
  • Master Thesis
    Manufacturing and Characterization of Perovskite Thin Films Using Novel Methods
    (Izmir Institute of Technology, 2020) Bıyıklı, Ozan; Sarı, Emre; Tekin, Hüseyin Cumhur
    Perovskite photovoltaics is a promising technology due to its low-cost fabrication and high efficiency. Since their first demonstration in 2009, efficiencies of perovskite solar cells (PSCs) increased unprecedently fast from 3.81% to 25.2% in 10 years. The most common method for the deposition of the absorber layer of the perovskite solar cells is the spin-coating method, which is not a scalable method, and this method is an obstacle to their commercialization. Efficiencies obtained with scalable methods are currently lower than that of the spin-coating method. In this thesis, among the scalable deposition methods, a novel ultrasonic spray-coating was used by adding antisolvent vapor to the system. The antisolvent quenching technique, that is commonly used to improve the crystalline quality of the film by spin-coating was successfully adapted for ultrasonic spray coating. The interaction between diethyl ether (DE) vapor, which is used as an antisolvent, and MAPb(I(3-x)Brx)3 precursor solution (where the solvent is DMF:DMSO, 4:1) was utilized to improve the crystalline quality of the perovskite film. As a result of this interaction, the intermediate phase was observed. The transition to the intermediate phase is supported by data from characterization methods such as optical microscopy, scanning electron microscopy (SEM), X-Ray diffraction (XRD), and current-voltage measurement. Furthermore, n-i-p devices with the FTO/c-TiO2/m-TiO2/MAPb(I(1-x)Brx)3/Spiro-OMeTAD architecture were produced with different antisolvent vapors and their efficiencies was compared. It was observed that devices using DE vapor reach higher efficiencies than devices without any antisolvent vapor.
  • Master Thesis
    Anti-Reflective and Optical Transparent Coatings for Thin Film Solar Cells and Glasses
    (Izmir Institute of Technology, 2020) Kamolov, Shukrullo; Özyüzer, Lütfi; Özyüzer, Lütfi
    Antireflective coatings in some implementation necessary for the decreasing surface reflection, but in some applications also for increasing transmittance. Incident radiation on the surface of the optical material is divided into transmitted, reflected, scattered, and absorbed proportions, and the proportion of current energy that deployed among them is defined by RI (refraction indices). Solar panels made from crystalline or polycrystalline silicon, but another type of solar panel is a thin-film solar panel. Thin-film technology has several advantages, such as low material consumption, which leads to cost savings to production, the ability to absorb diffused solar radiation, a relatively high efficiency (up to 20%), long service life (efficiency decreases by 10-15% of the initial efficiency). For all types of photovoltaic devices, energy loss is an important issue. Single-layer and two-layer antireflection coatings with a low refractive index, coated and uncoated (SiO2) thin-film with the sol-gel method were prepared and compared in terms of performance and continuity. The photocatalytic performance of (SiO2) thin films in 1, 2, 3, 4, 5 and 24 hours was defined with methylene blue dye solution (20 mL) under UV source and was illuminated by it. The I-V characteristics curve of solar cells for small and large area was learned and increasing efficiency was observed. Adhesion tests in this study was applied by tape tests on substrates of glass. As a result, the field tests of small and large area glasses coated solar panels were realized, the low reflectance and high efficiency were obtained.