Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Özyüzer, LütfiSubject: search.filters.subject.Magnetron sputtering

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  • 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
    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.