Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 2Citation - Scopus: 2Investigation of the Effect of Thermal Cycling on the Device Performance of Yba2cu3o7-? Dc-Squids(IOP Publishing Ltd., 2007) Avcı, İlbeyi; Algül, B. P.; Bozbey, Ali; Akram, R.; Tepe, Mustafa; Abukay, DoğanWe investigated the effect of thermal cycling on the operational performance of YBa2Cu3O7-δ (YBCO) direct current superconducting quantum interference devices (DC-SQUIDs) fabricated onto 24°SrTiO3 (STO) bicrystal substrates. The devices under investigation consist of directly coupled DC-SQUID magnetometer configurations. Thin films having 200nm thicknesses were deposited by dc-magnetron sputtering and device patterns were made by a standard lithography process and chemical etching. The SQUIDs having 4νm-wide grain boundary Josephson junctions (GBJJs) were characterized by means of critical currents, peak-to-peak output voltages and noise levels, depending on the thermal cycles. In order to achieve a protective layer for the junctions against the undesired effects of thermal cycles and ambient atmosphere during the room temperature storage, the devices were coated with a 400nm thick YBCO layer at room temperature. Since the second layer of amorphous YBCO is completely electrically insulating, it does not affect the operation of the junctions and pick-up coils of magnetometers. This two-layered configuration ensures the protection of the junctions from ambient atmosphere as well as from the effect of water molecules interacting with the film structure during each thermal cycle.Article Citation - WoS: 5Citation - Scopus: 6Effect of Deposition Conditions on Yba2cu3o 7-? Thin Films by Inverted Cylindrical Magnetron Sputtering and Substrate Effects(Elsevier Ltd., 2004) Avcı, İlbeyi; Tepe, Mustafa; Abukay, DoğanThe dependence of YBCO thin film properties on the deposition conditions was studied for different substrates. The deposition conditions were optimized for the epitaxial growth of high quality YBCO thin films of 1500 Å thickness onto single crystal (100-oriented) SrTiO3 (STO), MgO and LaAlO3 (LAO) substrates by DC Inverted Cylindrical Magnetron Sputtering (ICMS). The samples were investigated in detail by means of X-ray diffraction analysis (XRD), EDX, AFM, ρ-T, magnetic susceptibility and current-voltage (I-V) characterizations. The samples show strong diamagnetic behavior and sharp transition temperatures of 89-91 K with ΔT < 0.5 K. XRD of the samples exhibited highly c-axis orientation. The full width at half maximum (FWHM) values of the rocking curves were ranging typically from 0.22 to 0.28°. The samples have smooth surfaces as shown from AFM micrographs. The surface roughness, Ra, changed between 5-7 nm. I-V characteristics were obtained from the 20μm-wide microbridges, which were patterned by a laser writing technique. The critical current densities (Jc, 1.06 × 106 for LAO-based YBCO, 1.39 × 106 for MgO-based YBCO, 1.67 × 106A/cm2 for STO based YBCO) of the microbridges were evaluated from I-V curves at 77 K.