Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 TechnologyVanadium 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 Hydrothermal Synthesis and Characterization of Vanadium and Tungsten Oxide Containing Organic-Inoganic Hynrid Material(Izmir Institute of Technology, 2011) Önen, Banu; Emirdağ Eanes, Mehtap; Eanes, Mehtap; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of TechnologyHydrothermal synthesis of transition metal oxide containing organic-inorganic hybrid materials has attracted great attention recently. Two novel organic-inorganic hybrid materials (4,4’-bipy)3[HPW12O39] and [Cu(4,4’-bipy)4][HPW12O40] were hydrothermally synthesized as green and purple crystals respectively, from the reaction of Na6[H2W12O40], CuCl2.2H2O, 4,4’- bipyridine and H3PO4 in a 23 ml autoclave at 170°C for 72 hours. The compound (4,4’- bipy)3[HPW12O39] crystallizes in the space group P21/n of the monoclinic system with four formula units in a cell with dimensions a = 13.503(3) Å, b = 26.726(5) Å, c = 15.169(3) Å and V = 5397.3(19) Å 3 . [Cu(4,4’-bipy)4][HPW12O40] crystallizes in the space group Pbcn of the tetragonal system with eight formula units in a cell of dimensions a = 20.236(4) Å, b = 25.635(5) Å, c = 20.236(4) Å; V = 10497(4) Å 3 . Both of the compounds are Keggin polyoxometalate structures. (4,4’-bipy)3[HPW12O39] contains free 4,4’-bipy groups among the clusters while in [Cu(4,4’-bipy)4][HPW12O40] 4,4’-bipy ligands are coordinated to Cu 2+ ions. A novel compound (H2NC4H8NH2)[(VO)2(PO4)2] was synthesized hydrothermally from the reaction of NaVO3, V2O5, ethylenediamine and H3PO4 at 170°C for 72 hours. The compound crystallizes in the space group P-1 of the trigonal system with five formula units in a cell of dimensions a= 6.3345(13) Å, b= 6.3353(13) Å, c= 15.940(3) Å, V=639.6(2) Å 3 . (H2NC4H8NH2)[(VO)2(PO4)2] displays a layered structure with protonated piperazine groups between layers. In addition to the novel compounds, several known compounds were synthesized as well. Blue crystals of (VO)(H2PO4)2 were obtained hydrothermally from the reaction of NaVO3, ethylenediamine and H3PO4 at 170°C for 72 hours. (C5NH6)4.5(H3O)1.5[P2W18O62] , a known compound also, was synthesized from the reaction of Na2WO4 .2H2O, CuCl2.2H2O, pyridine and H3PO4 at 170°C for 72 hours