WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
5 results
Search Results
Now showing 1 - 5 of 5
Article Citation - WoS: 3Citation - Scopus: 3Mgb2 Superconducting Thin Films Grown by Magnetron Sputtering(National Institute of Optoelectronics, 2007) Ulucan, Savaş; Özyüzer, Lütfi; Okur, SalihIn this study, we report the growth and properties of MgB2 thin films on polycrystalline Al2O3 substrates. A composite MgB2 target was produced by MgB2 and Mg powder mixing, using a hot pressing technique. MgB2 thin films were grown on Al 2O3 substrates by d.c. magnetron sputtering, without heating the substrate. To enhance the superconducting properties of the as-grown films and to increase the crystal quality, an ex-situ anneal process was applied. The crystal structure of the thin films was determined by X-ray diffraction. The resistivity versus temperature of the deposited MgB2 thin films was studied to examine the transition temperatures of the films under various magnetic fields. The effects of the annealing temperature and annealing time on the electrical properties of MgB2 thin films are revealed.Conference Object Citation - WoS: 3Citation - Scopus: 2Fabrication of Superconducting Mgb2 From Boron Oxide (b 2o3), and Its Microstructural and Electrical Characterization(National Institute of Optoelectronics, 2005) Yavaş, Mert; Okur, Salih; Eğilmez, Mehmet; Kalkancı, Mihriban; Özyüzer, LütfiThe discovery of superconducting MgB2 (39 K) draws attention to it as a new material for applications based on superconductivity. Many researchers successfully synthesized MgB2 using commercial boron and magnesium. In this study, elementary boron was obtained via an acid leaching process, after reacting B2O3, and Mg in an argon atmosphere at 800°C. Energy Dispersive X-ray Spectroscopy (EDX) results revealed that the powder obtained from the reaction was boron in 92% purity with magnesium as the major impurity. Superconducting MgB2 was produced from this boron and magnesium, in an argon atmosphere at 900°C, by a conventional solid-state reaction. Superconducting MgB2 powders were compressed in a dye to pellets by a hot pressing technique at 500°C and 1 GPa. The microstructural properties of the MgB2 were determined by X-ray Diffraction Spectroscopy, EDX, and Scanning Electron Microscopy techniques. The electrical properties of the fabricated MgB 2 were examined by resistivity measurements in a closed-cycle cryopump system, between 20 and 300 K. The critical temperature (Tc) of the MgB2 pellets was around 32 K.Conference Object Citation - WoS: 7Citation - Scopus: 8Properties of Reactive O2 Ion Beam Sputtered Tio2 on Si Wafers(National Institute of Optoelectronics, 2005) Ulucan, Savaş; Özyüzer, Gülnur Aygün; Özyüzer, Lütfi; Eğilmez, Mehmet; Turan, RaşitTiO2 thin films were deposited on silicon (100) p-type wafers, using the reactive ion beam sputtering method in high vacuum as an alternative to conventional Argon ion beam sputtering in an O2 environment. Oxygen ions with 1000 eV energy were formed in a thruster and bombarded a high purity Ti target. The molecules of TiO2 were deposited on a Si (100) wafer at various substrate temperatures. The structural and optical properties were analyzed using Fourier Transform Infrared Spectroscopy in the range of 400-4000 cm-1. An ellipsometer was used to measure the thickness and refractive index of the deposited films. In order to determine the dielectric constant and capacitance of the deposited TiO2, the electrical properties were studied using an MOS capacitor. The effects of substrate temperature and deposition time on the dielectric properties of TiO2 are discussed.Conference Object Citation - WoS: 2Citation - Scopus: 2Microstructural and Electrical Characterization of Ti and Mg Doped Cu-Clad Mgb2 Superconducting Wires(National Institute of Optoelectronics, 2005) Okur, Salih; Kalkancı, Mihriban; Yavaş, Mert; Eğilmez, Mehmet; Özyüzer, LütfiThe recent studies on Ti doping effect on the critical current density (Jc) of MgB2 composite superconductors prepared under ambient pressure has shown an important enhancement at 20 K. In the present work, we have fabricated Ti and Mg doped superconducting MgB2 wires by packing reacted MgB2 and Ti or Mg powders together inside Cu tubes with a diameter of 6 mm. The tubes were then cold worked by rolling or drawing to smaller diameters. The prepared Cu-clad Ti and Mg added MgB 2 superconducting wires were annealed at various temperatures to enhance the grain connectivity of the MgB2 bulk materials. The effect of the sintering time has been investigated for high performance characteristics of superconducting Cu-clad Ti and Mg added MgB2 wires. The microstructural evaluation of the superconducting wires has been carried out using XRD and SEM equipped with EDX analysis system. The interfacial properties between Cu sheath and superconducting core was characterized using SEM-EDX. Furthermore, the influence of the presence of Ti and Mg on Tc has been investigated to understand the structural and electronic properties of superconducting Ti and Mg doped MgB2 wires.Conference Object Citation - WoS: 6Citation - Scopus: 6Fabrication of Array of Mesas on Superconducting Bi2sr 2cacu2o8+? Single Crystals(National Institute of Optoelectronics, 2005) Kurter, Cihan; Özyüzer, LütfiThe superconducting properties of multi-layered high temperature superconductors (HTS) result mainly from the CuO2 planes, while the other structural components behave simply as charge reservoirs. Using these perfect-layered structures of HTS, arrays of mesas have been fabricated on the surfaces of Bi2Sr2CaCu2O8+δ (Bi2212) single crystals using hotolithography and argon ion beam etching techniques. These arrays have current-voltage (I-V) characteristics that consist of some branches corresponding to different intrinsic Josephson junctions in the mesas, The surface topography and heights of the mesas were examined with atomic force microscopy. Due to the small mesa area, conventional wire bonding techniques are not applicable. A novel method, point contact tunneling apparatus with a sharp Au tip, was used to obtain the I-V characteristics of the fabricated intrinsic Josephson junctions, below the critical temperature of Bi2212. Since the ultimate goal was to obtain an ordered group of mesas with small lateral dimensions, to eliminate heating effects during I-V measurements, we showed that submicron-sized mesas could be characterized by the new technique.