Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Materials Science and EngineeringSubject: search.filters.subject.Thin films

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Now showing 1 - 4 of 4
  • Master Thesis
    Investigation of Sulfurization Temperature Effects on Cu2znsns4 Thin Flims Prepared by Magnetron Sputtering Method on Flexible Titanium Foil Substrates for Thin Flim Solar Cells
    (Izmir Institute of Technology, 2017) Buldu, Dilara Gökçen; Aygün, Gülnur; Aygün Özyüzer, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    This thesis presents the effect of sulfurization temperature on Cu2ZnSnS4 (CZTS) thin films on flexible titanium (Ti) foil substrates. The CZTS films was produced by using a two-stage method. In the first step, the metallic precursor layers Cu/Sn/Zn/Substrate were deposited on Ti foil substrate by using DC magnetron sputtering method. In the second step, the deposited metal precursors were sulfurized in a graphite box under Argon (Ar) ambient inside a tubular furnace under a definite temperature. To understand the effects of temperature on the formation of the CZTS structure several analyses were performed. Our samples, each with a different sulfurization temperature; ranging from 530 to 580 oC, were carried out and the structural properties of the absorber layer was determined. XRD measurements showed a sharp and intense peak coming from the (112) planes which was a strong evidence for good crystallinity. The intensity of (112) plane became a sharp and intense with increasing sulfurization temperature. Raman spectroscopy of the sulfurized thin films revealed that, the kesterite structure CZTS thin film were obtained with increasing sulfurization temperature. Electron Dispersive Spectroscopy (EDS) was also used for the compositional analysis of the thin films. EDS analysis showed that the films were grown with a Cu-poor Zn-rich composition. From these analyses we conclude that no interface formation occurred between the substrate and the CZTS thin films, hence, a buffer layer was not required. It was also seen that Ti foil was suitable as substrate for the growth of CZTS thin films with desired properties. We also conclude that the sulfurization temperature plays a crucial role for producing good quality CZTS thin films on Ti foil substrate.
  • Master Thesis
    Self-Organized Network of Silicon Oxide on Epitaxial Graphene
    (Izmir Institute of Technology, 2017) Özkendir, Dilce; Çelebi, Cem; Çelebi, Cem; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this thesis, I studied the formation and characterization of self-organized hexagonal-shaped SiO2 wrinkle structures on epitaxial graphene that was grown on SiC substrate. Monolayer graphene was grown by annealing the SiC substrate at high temperatures under ultra-high vacuum conditions. Following the growth process, SiO2 thin film was deposited on epitaxial graphene layer at different deposition temperatures by thermal evaporation method. We found that SiO2 film wrinkles on epitaxial graphene. The origin of the hexagonal shaped wrinkle structures were derived from the thermal expansion coefficient difference between epitaxial graphene and SiO2 thin film. The mesh density of these SiO2 hexagonal wrinkle structures was controlled by changing the cooling rate of the substrate after the thin film deposition. To make a comparison, SiO2 thin film was also deposited on CVD grown graphene and on bare SiC substrate. Unlike on the bare SiC surface, SiO2 thin film on epitaxial graphene exhibited a self-assembled network of hexagonally shaped wrinkles due to thermally induced compressive strain between the two materials. The observed network of wrinkles were found to be comprised of line shaped primary and secondary types of protrusions with distinct topographic characteristics as determined by optical microscopy, Scanning Electron Microscopy and Atomic Force Microscopy measurements. The wrinkle to wrinkle spacing and mesh density of the wrinkle network were modified simply by changing the SiO2 deposition temperature. Our experimental results imply that epitaxial graphene with its high chemical inertness on SiC offers a great potential to be used as a conventional substrate in the realm of thin film metrology.
  • Master Thesis
    Ionic Conductivity of Li0.5la0.5ti1-Xalxo3 Electrolytelayer for Thin Film Batteries
    (Izmir Institute of Technology, 2016) Ulusoy, Seda; Özyüzer, Lütfi; Aral, Gürcan; Özyüzer, Lütfi; Aral, Gürcan; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study, crystalline lithium lanthanum titanium (aluminum) oxide Li0.5La0.5Ti1-xAlxO3 (LLTO) powder targets with different Aluminum (x) content were prepared by conventional solid state reactions as Li0.5La0.5TiO3, Li0.5La0.5Ti0.99Al0.01O3, Li0.5La0.5Ti0.95Al0.05O3, Li0.5La0.5Ti0.90Al0.10O3 and Li0.5La0.5Ti0.85Al0.15O3 compositions. Then, after a couple of calcination processes with regrinding of the prepared stoichiometric powder batch, it is placed into Cu-base plate to be pressed in order to provide a compact, dense and smooth target surface for the thin film deposition. For the thin film fabrication, radio frequency (RF) magnetron sputtering technique is used to sputter the dielectric target. Thin films were deposited on soda-lime glass (SLG) and 256 nm thick indium tin oxide (ITO) layer grown on soda-lime glass (SLG) substrates. For the electrical measurements of LLTO thin film, it was fundamental to have ITO as conducting layer electrode. Targets with various Al (x) compositions were deposited for the investigation of Ti substitution with Al on structural and electrical properties. Besides, crystalline structure of the targets was characterized by X-ray powder diffraction (XRPD) and Raman Spectroscopy analysis while structural, morphological and compositional properties of the thin films were determined by x-ray diffraction (XRD), scanning electron microscope (SEM) and x-ray photoelectron spectroscopy (XPS) respectively. Moreover, in order to understand the effect of Al doping on ionic conductivity, electrical measurements were performed at room temperature by AC impedance spectroscopy forming ITO/LLTO/Al capacitor like structure. Maximum ionic conductivity result is obtained for Li0.5La0.5Ti0.95Al0.05O3 thin film composition. Also, temperature dependent ionic conductivity measurements were performed from 298 K to 373 K to evaluate activation energy for the Li-ion conduction. Keywords: Ionic conductivity, Li0.5La0.5Ti1-xAlxO3, electrolyte, thin film, activation energy, RF magnetron sputtering
  • Master Thesis
    Thin Film Coating of Silver on Fibers by Roll To Roll Inverted Cylindrical Magnetron Sputtering
    (Izmir Institute of Technology, 2015) Taşdemir, Adnan; Özyüzer, Lütfi; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    There is a huge demand in functional textile product by the advent of nanotechnology and thin film technology. Antistatic and antibacterial textile materials are highly required in medical centers, clean rooms, military basis and electronic device manufacturers. Moreover, these materials are increasingly studied in many scientific committees by several method. Functional textile fabrics can be produced by surface finishing or adding conductive fibers. Many methods are employed to obtain conductive fiber but Physical Vapor Deposition (PVD) offer better homogeneity and high efficiency when compared to Chemical Vapor Deposition (CVD) methods. Magnetron sputtering is the industrial scale thin film production technique among PVD methods. However, mainly used planar magnetron sputtering systems do not enable samples to be coated all sides of cylindrical surface of a fiber so that an inverted cylindrical magnetron (ICM) sputtering system was designed for this research. ICM system was optimized and operated to deposit silver thin film on all sides of PA fibers which have diameters 85 and 150 um. A continuous roll to roll mechanism was mounted to system that enables to metalize fibers at high speed continuously. Conductive fibers are proposed to be produced at industrial scale. XRD, SEM and optical microscopy characterizations are employed on silver thin film coated polyamide fibers. In order to obtain thin film thickness of fibers, they are investigated by three different methods which can be calculating from i) bulk resistivity formula by using measured resistance, ii) deposited silver mass by using density of silver and iii) system calibration sample which is basically sending a glass lamella with same sputtering parameters and measuring sputtered thin film on it. These all results were compared to find optimum thickness. These conductive fibers woven in synthetic fabrics to promote them antistatic and shielding property. Antistatic and adhesion analysis of these fabrics are investigated and surface resistance and shielding property of fabrics were studied. All in all, these fabrics will be used as technical textile which is presumed to satisfy demands.