Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, PhysicsSubject: search.filters.subject.Thin films

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  • 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) Özyüzer, Lütfi; Özdemir, Mehtap; Özyüzer, Lütfi; Özdemir, Mehtap; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    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) Aygün, Gülnur; Özyüzer, Gülnur Aygün; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    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; Aygün, Gülnur; Özyüzer, Gülnur Aygün; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    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
    The Growth of Vanadium Dioxide Thin Films by Magnetron Sputtering Technique and Terahertz Wave Modulation Characteristics
    (01. Izmir Institute of Technology, 2020) Özyüzer, Lütfi; Ata, Bengü; Özyüzer, Lütfi; 01. Izmir Institute of Technology; 04.05. Department of Pyhsics; 04. Faculty of Science
    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
    Improvement of Transparent Conductive Hybrid Ito/Ag Electrodes by Electro-Annealing
    (Izmir Institute of Technology, 2019) Uyanık, Zemzem; Uyanık, Zemzem; Aygün, Gülnur; Aygün Özyüzer, Gülnur; 04.05. Department of Pyhsics; 01. Izmir Institute of Technology; 04. Faculty of Science
    Hibrit ITO/Ag/ITO (IAI) ince film tabaka yapılarının optik ve elektriksel performansları, ITO ve Ag katmanı kalınlığının fonksiyonu olarak incelenmiştir. Hibrit IAI ince filmleri borosilikat cam üzerine oda sıcaklığında yüksek vakum altında dc mıknatıssal saçtırma yöntemi ile üretilmiştir. Hibrit yapıdaki ITO, Ag, ITO filmlerin kalınlığı düşük tabaka direncine ve yüksek optik geçirgenliğe sahip olacak şekilde ayarlanmıştır. ITO katmanları arasındaki gömülü metal Ag katmanı, 10 nm ile 25 nm arasında değişen kalınlıklarda kullanılmıştır. IAI tabakası analiz edildikten sonra IAI ince filmlerin kristalliğini iyileştirmek için elektro-tavlama uygulanmıştır ve elektrik akımının IAI ince filmler üzerindeki etkisinin araştırılmasıyla elektronik cihaz ömrünün arttırılması amaçlanmıştır. Elektro-tavlamanın endüstriyel uygulamalar için daha uygun bir teknik olduğu sonucuna varılmıştır. IAI ince filmin yüzey direnci elektro-tavlama işleminden sonra 8.7 Ω/□ olarak bulunmuştur en yüksek geçirgenliğe ise 88.9% da ulaşılmıştır. Hibrit IAI ince filmlerin optoelektronik özellikleri, ITO film kristalliğini etkileyen ara katman olan metal Ag kalınlığına bağlıdır. Hibrit IAI ince filmlerinin yapısal özellikleri, CuK����� radyasyonuna sahip (�����=0.154 nm) X-ışını kırınımı (XRD) (Philips X'Pert Pro) ile tavlama sıcaklığının fonksiyonu olarak karakterize edilmiştir. IAI ince filmlerinin morfolojisi hakkında bilgi taramalı elektron mikroskobu (SEM) ile elde edilmiştir. IAI ince filmin optik geçirgenliği 200-2600 nm dalga boyu aralığına sahip PerkinElmerLambda 950 UV/Vis/NIR Spektrofotometre ile ölçülmüştür. Yüzey direnci ölçümleri için Keithley 2424 kaynak metrisi kullanılarak dört nokta yöntemi uygulanmıştır.
  • Master Thesis
    Temperature Dependence of Resistivity and Hall Coefficient in Cu2znsns4 Absorbers for Thin Film Solar Cells
    (Izmir Institute of Technology, 2017) Akça, Fatime Gülşah; Aygün, Gülnur; Özyüzer, Lütfi; Aygün Özyüzer, Gülnur; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    energy is the most powerful clean energy source to act on the current energy needing all over the world. The utilization of green energy systems should be promoted since these energy systems benefit consumers, industry and the environment effectively for the developing countries. This advancement can be solely achieved if renewable energy sources become more accessible. It means that not only cheaper but also handy clean energy systems are needed. In spite of relatively high efficiency obtained by using c-Si, Si solar modules require high budget for manufacturing. The high production cost of c-Si, PV industry is lead to search for cheaper candidate materials like Cu2ZnSnS4 (CZTS) as absorber layer in solar cells. The aim of the thesis is to investigate electrical properties of CZTS p-type intrinsic semiconductor compound on soda lime glass substrates, including the temperature dependent electrical conductivity, carrier concentrations and mobility extracted from Hall Effect measurements. Firstly, the metal precursor films were fabricated in multi-target sputtering system, then they were sulfurized inside the tubular furnace in order to obtain the CZTS compound. X-ray diffraction and Raman spectroscopy measurements revealed the formation of kesterite structure. A good crystallinity and grain compactness of the films were determined by scanning electron microscopy (SEM). Electrical properties were measured by van der Pauw techniques. Hall effect measurements showed the p-type semiconductor behavior for all samples at room temperature. Also, optical properties including absorption coefficient, spectral transmission, and optical band gap were determined to characterize CZTS thin films.
  • Master Thesis
    Properties of Thin Film Lixlaytio3 Electrolyte for All-Solid State Li-On Batteries
    (Izmir Institute of Technology, 2016) Gülen, Sena; Aygün, Gülnur; Aygün Özyüzer, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    One of the requirements of daily life, the most preferred rechargeable batteries are Li-ion batteries because of high energy, long life cycle and eco-friendly properties. Having high energy density, no memory effect and slow energy losses, these batteries have applications in portable electronic devices, power source for space vehicles, electric cars etc. Furthermore, there is a strong interest in all solid-state rechargeable lithium-ion battery research, because these batteries will replace the conventional liquid electrolyte Li-ion batteries due to use of non-combustible inorganic solid electrolyte, which has high safety and reliability. While the bulk ionic conductivity of La0.5Li0.5TiO3 (LLTO) produced by solid-state reaction is 10-3 S/cm, the total ionic conductivity of LLTO is 10-5 S/cm. Another way to increase ionic property is to dope the solid electrolyte with transition metals. The substitution of transition metal leads to decrease of the lattice parameter because of reduced average ionic radius. This causes increase of Li-ion content and also ionic conductivity. In this study, initially pure and Al doped targets were fabricated by using solid-state reaction after that the available targets are placed to the sputtering gun. When the all optimizations of the system were completed, pure and Al doped LLTO thin films were deposited by RF (radio frequency) magnetron sputtering technique on ITO coated soda lime glass substrates. While the thin film was been deposited, the substrate was heated at approximately 220 oC. For ionic conductivity measurement of the Al doped LLTO electrolyte, small circular Al contact regions were created on Al doped LLTO thin films by thermal evaporation system. Afterword the impedance spectra of the sandwich structure in a frequency range of 1 Hz - 200 MHz was recorded by using probe station. Thickness, the crystal structure, optical transmission, chemical compositions, surfaces and porosity of the thin films are investigated by surface profilometer, XRD, UV-Visible Spectroscopy, XPS, and Raman Spectroscopy respectively.
  • Master Thesis
    Characterization of Vanadium Oxide Thin Films Grown by Magnetron Sputtering Technique
    (Izmir Institute of Technology, 2015) Yüce, Hürriyet; Yüce, Hürriyet; Özyüzer, Lütfi; Özyüzer, Lütfi; 03.09. Department of Materials Science and Engineering; 04.05. Department of Pyhsics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Vanadium dioxide (VO2) exhibits metal insulator transition (MIT) at around 70 °C. VO2 shows insulator phase at low temperature whereas above the transition temperature VO2 shows metallic phase. The resistivity of this material abruptly changes by a factor of 104 at MIT temperature. There are some factors which induce MIT in VO2 structure such as electric field, the change in temperature or doping. Due to these properties, VO2 is an interesting candidate for exploring potential applications in high speed electronic devices. VO2 plays an important role for field effect transistor (FET) applications. VO2 with its peculiar properties is a good candidate for channel material in FET. Electric field triggered MIT is a desired feature for FET applications. In this work, VO2 thin films have been deposited on c-cut sapphire [Al2O3(0001)] substrate by using DC magnetron sputtering technique. In order to obtain the homogeneous VO2 thin film, the growth process was carried out at various oxygen flow rates with different deposition time. To obtain single VO2 phase, optimum oxygen rate was investigated with various analysis techniques such as Raman, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and optical-electrical measurements. At the same time, the temperature dependences of optical-electrical properties of these films were analyzed. Then, the metal insulator transition was observed with the change in resistivity by a factor of 104 which is the highest value among grown VO2 films by sputtering technique in the literature. For FET applications, the grown VO2 thin film which indicates the highest change in resistivity at transition temperature was patterned by electron beam lithography in order to create FET channel schema. After electron beam lithography process, the electrical properties of the VO2 strips with various widths were analyzed. The effects of the widths of the VO2 strips on their electrical properties were investigated.
  • Master Thesis
    Defect Reduction Study of Molecular Beam Epitaxially Grown Cdte Thin Flims by Ex-Situ Annealing
    (Izmir Institute of Technology, 2015) Bakali, Emine; Selamet, Yusuf; Selamet, Yusuf; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Molecular Beam Epitaxy (MBE) grown CdTe thin films were annealed in this study to decrease the number density of defects. For annealing, a system was designed and constructed. During anneals; anneal temperature, anneal time, anneal cycle and hydrogen gas effects were analyzed. The effects of annealing parameters were analyzed by Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), Everson Etch method, resonance Raman spectroscopy and Photoluminescence measurement. In our studies, dislocation density decreased for 5 min. annealing when annealing temperature increased. Dislocation density decreased with increasing annealing time. Besides, dislocation density decreased when cycle number increased. Te precipitation decreased with annealing. Raman mode at 144 cm-1 was investigated and that mode was decided as Te E mode. Also I2LO/ILO ratio decreased with increasing annealing temperature and annealing time. I2LO/ILO ratio were approached to 1 at 80oK due to so called ‘resonance Raman scattering’. Extra peaks were also observed by Raman scattering. On the surface, small pits occurred when annealing temperature increased. Surface roughness decreased with increasing cycle number.
  • Master Thesis
    Indium Tin Oxide (ito) Coating on Cylindricalsurfaces: Electrical and Structural Characterization
    (Izmir Institute of Technology, 2015) Aral, Gürcan; Aral, Gürcan; Özyüzer, Lütfi; Özyüzer, Lütfi; Aral, Gürcan; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Optical transparent conductive oxides (TCOs) which were discovered in the first quarter of twentieth century, and which belong to the class of semiconductor elements, are the constituent of today’s and future technology thanks to the high optical transparency ( ≥ % 85) they have in the visible region (390- 700 nm), and to the low electrical resistivity they have (10-4 ohm.cm). One of the most common usage of optical transparent conductive oxides; which have a quite extensive application area from transistors to solar panels, from flexible screens to OLEDs; is the textile materials known as smart clothes. The use of TCOs in textile materials, generally occurs by means of electrochromic structures that have the feature of changing color. In the most general sense, electrochromic structures can be defined as the materials that change their colors, which they gain thanks to reduction and oxidation reactions under a low potential difference of 1.5 – 5V, as a transition from one color state to another or from colorless state to color state. Even though they differ according to their area of utilization, electrochromic structures are generally consisted of seven layers as; Surface / conductive thin film (TCO) / Electrolyte film / Ionic conductive layer / Opposite electrolyte film / Conductive thin film (TCO) / and Surface. Electrical conductor and optical transparent indium doped tin oxide (ITO) film that are of vital importance in electrochromic fiber structures, were deposited on the fiber surface along with the specially-designed magnetic sputter in order to coat the cylindrical surfaces within the scope of the thesis. Film deposition was repeated by replacing the ionizing gas (Ar) flow rate and the energy applied. While the structural characterization of thin films was carried out by means of optical microscope and scanning electron microscope (SEM), electrical characterization of deposited thin film, was carried out by a multi-meter (Ohm meter). In addition, the thickness of thin film that was magnified on the surface of the fiber, was calculated by SEM particularly, and also by different methods. As a result of the analyzes carried out, it was observed that ~ 40 sccm ionizing gas flow rate, 90 W applied energy, and 119 cm/min fiber feed rate increased the quality of the thin film acquired.