Abukay, Doğan
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Abukay, D.
Abukay, Dogan
Abukay, D
Abukay, Dogan
Abukay, D
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abukay@gmail.com
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04.05. Department of Pyhsics
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Former Staff
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33
Citations
191
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This researcher does not have a WoS ID.
Scholarly Output
18
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10
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14232/8714
Supervised MSc Theses
6
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WoS Citation Count
100
Scopus Citation Count
105
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2
WoS Citations per Publication
5.56
Scopus Citations per Publication
5.83
Open Access Source
18
Supervised Theses
6
| Journal | Count |
|---|---|
| Superconductor Science and Technology | 2 |
| Solid State Communications | 2 |
| IEEE Transactions on Applied Superconductivity | 1 |
| Journal of Alloys and Compounds | 1 |
| Physica C: Superconductivity and its Applications | 1 |
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18 results
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Now showing 1 - 10 of 18
Master Thesis Fabrication and Characterizarion of Superconductor Ybco Josephson Junctions(Izmir Institute of Technology, 2008) Algül, Berrin Pınar; Abukay, Doğan; Abukay, DoğanA well-controlled, high-yield Josephson junction production process forms the basis of superconducting electronic device and circuit technology. In order to use the Josephson junctions effectively and fabricate them reproducibly, their structural and electrical characterization should be performed.This study concentrates on the fabrication and characterization of high temperature bicrystal grain boundary Josephson junctions fabricated onto 24-dand 30-degree SrTiO3 bicrystal substrates using high quality YBa2Cu3O7-. (YBCO) thin-films.200 nm thick YBCO thin films were deposited using a dc Inverted Cylindrical Magnetron Sputtering technique by investigating the thin film deposition conditions in order to obtain device quality films. The superconducting properties of the thin films were determined by electrical characterizations, consisting of resistance versus temperature and magnetic susceptibility versus temperature measurements. Structural properties were analyzed by Atomic Force Microscope, Scanning Electron Microscope and X-Ray Diffraction.Prepared thin film samples were patterned as bicrystal grain boundary Josephson junctions by standard photolithography and chemical etching processes. The current-voltage characteristics of the Josephson junctions were performed at 77 K under zero and non-zero applied field in magnetically shielded environment. The critical current values (Ic), normal resistance (Rn) and IcRn product of the output signals were determined, and the values were discussed as function of the film growth conditions. The optimization of the Josephson junctions was performed in order to improve both the signal performance and the stability of our devices against thermal cycling.Article Citation - WoS: 2Citation - Scopus: 4Signal Performance of Dc-Squids With Respect To Ybco Thin Film Deposition Rate(Elsevier Ltd., 2009) Avcı, İlbeyi; Algül, Berrin Pınar; Akram, Rizwan; Bozbey, Ali; Tepe, Mustafa; Abukay, DoğanThe signal performances of YBa2Cu3O7-δ (YBCO) direct current superconducting quantum interference devices (DC-SQUIDs) have been investigated as a function of the thin film structure affected by the growth process. YBCO thin films of 200 nm thicknesses were deposited by DC magnetron sputtering using different deposition rates between 1.0 nm/min and 2.0 nm/min onto 24° bicrystal SrTiO3 (STO) substrates. The thin film samples were subsequently analyzed by XRD and AFM in order to determine their crystalline structures and surface morphologies respectively. The 67 pH directly coupled DC-SQUIDs with 4 μm-wide bicrystal Josephson junctions were fabricated, and characterized with respect to their device performances. The variations in the critical current (Ic), the voltage modulation depth (ΔV) and the noise performance of DC-SQUIDs were reported. The SQUIDs having relatively low deposition rate of 1.0 nm/min was observed to have larger voltage modulation depth as well as higher critical current than that of the samples having larger rate of 2.0 nm/min. The better noise performances were observed as the film deposition rate decreases. The results were associated with the thin film structure and the SQUID characteristics.Master Thesis High Temperature Superconducting Yba2cu3o7-X Transitation Edge Bolometers (tebs) for Infrared Region(Izmir Institute of Technology, 2008) Günel, Hacı Yusuf; Abukay, Doğan; Abukay, DoğanThe thesis focuses on electrical and bolometric characterization of high temperature superconducting YBCO transition edge bolometers. In this study, superconducting YBCO thin films grown on MgO, LaAlO3 and SrTiO3 substrates were first characterized structurally via x-ray diffraction and scanning electron microscopy.They then were patterned into bolometers and their electrical and bolometric characterizations were carried out. The results of these characterizations were fitted to the RC model. In addition, figures of merit for these devices, such as noise equivalent power (NEP) and detectivity, were measured and calculated.During this work, the patterning process was carried out by standard photolithographic processes and chemical etching. We have also investigated the effect of dimensions of our devices on the performance of bolometers. The electrical and bolometric characterizations comprised of resistance versus temperature (R-T), amplitude of response versus temperature, amplitude of response versus chopping frequency (A-F) and noise voltage measurements. Finally, the performance of our devices were compared to literature and found to be similar to or better than those of similar devices in literature.Article Developing a Trilayer Processing Technique for Superconducting Yba 2cu3o7-? Thin Films by Using Ge Ion Implantation(IOP Publishing Ltd., 2005) Avcı, İlbeyi; Tepe, Mustafa; Öktem, Bülent; Serincan, Uğur; Turan, Raşit; Abukay, DoğanFor making trilayer superconducting devices based on YBa2Cu 3O7-δ (YBCO) thin film processing, we developed a new technique by employing Ge ion implantation. A YBCO thin film of 150 nm thickness having high c-axis orientation and a transition temperature, T c, of 90 K was implanted with 80 keV, 1 × 1016 Ge ions cm-2 at room temperature. By the result of TRIM calculation, Ge ions were found to penetrate into the YBCO thin film approximately 60 nm below the surface of the film, thus leaving the lower part of the film as a superconductor. Upon implantation with Ge ions, the implanted upper part of the sample lost its electrical conductivity and diamagnetism while its original crystalline structure was preserved. The implanted ions we found did not alter the overall crystal structure of the YBCO thin film; this allowed us to grow an epitaxial superconducting upper layer of YBCO on top of the implanted area, leaving no need to use any buffer layer. The superconducting properties of the upper layer were similar to those of the pure YBCO base layer with an increased room temperature resistivity and a lowered Tc (88 K). This process provides an effective method for fabrication of a trilayer HTS device structure.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.Conference Object Citation - WoS: 1Dependence of Josephson Junction Critical Current on the Deposition Rate of Yba2cu3o7-? Thin Films(American Institute of Physics, 2007) Algül, B. P.; Avcı, İlbeyi; Akram, R.; Bozbey, Ali; Tepe, Mustafa; Abukay, DoğanWe have reported the effect of YBa2Cu3O 7-δ (YBCO) thin film deposition rate on the 24 and 30 degree STO bicrystal Josephson junctions critical currents by fabricating series of junctions with different deposition rates. Dependence of YBCO thin film structures on the deposition rate was investigated. We have observed that the critical currents of junctions are strongly affected by the thin film deposition rate.Master Thesis Pixel Array Application of High Temperature Superconducting Ybco Transition Edge Infrared Bolometers(Izmir Institute of Technology, 2009) Pekerten, Barış; Abukay, DoğanIn this thesis, we patterned pregrown epitaxial YBCO thin films on MgO, LAO and STO substrates into meander shaped high-Tc superconducting transition edge monolithic bolometers. We set up and automatized the electrical characterization processes of the bolometers. We also measured the bolometric response of the meanders to red and nearinfrared light and fit them to theoretical models in literature. We compared the single pixel bolometric responses to literature and found that our results are similar to or better than the results for similar devices in the literature.We also patterned staring arrays (focal plane arrays) and explored the resolution limit put in place by thermal crosstalk. We compared the measured crosstalk to theory and found a very good agreement. We quantified the crosstalk for our pixels. We then explored substrate etching method to decrease crosstalk via thermal isolation.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: 18Citation - Scopus: 18The Effects of the Post-Annealing Time on the Growth Mechanism of Bi2sr2ca1cu2o8+ Thin Films Produced on Mgo (100) Single Crystal Substrates by Pulsed Laser Deposition (pld)(Elsevier Ltd., 2016) Nane, Onur; Özçelik, Bekir; Abukay, DoğanBi2Sr2Ca1Cu2O8+δï thin films were deposited on MgO (100) substrates by pulsed laser deposition (PLD). The effects of post-annealing time on the phase formation, the structural and superconducting properties of the films have been investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature dependent resistivity (R-T), atomic force microscopy (AFM), and DC magnetization measurements. The films deposited at 600 °C were post-annealed in an atmosphere of a gas mixture of Ar (93%) and O2 (7%), at 860 °C for 10, 30, and 60 min. All films have demonstrated a mainly single phase of 2212 with a high crystallinity (FWHM0.159°) and c-axis oriented. The critical temperature, TC, of the films annealed for 10, 30, and 60 min were obtained as 77, 78, and 78 K, respectively. The highest critical current density, JC, was calculated as 3.34×107 A/cm2 for the film annealed at 860 °C for 30 min at 10 K.Article Citation - WoS: 9Citation - Scopus: 10The Effects of the Post-Annealing Temperature on the Growth Mechanism of Bi2sr2ca1cu2o8+ ? Thin Films Produced on Mgo (1 0 0) Single Crystal Substrates by Pulsed Laser Deposition (pld)(Elsevier Ltd., 2013) Nane, O.; Özçelik, Bekir; Abukay, DoğanThe effects of post-annealing temperature were investigated on Bi 2Sr2Ca1Cu2O8+ ∂ thin films deposited on MgO (1 0 0) substrates by pulsed laser deposition (PLD). The structural and superconducting properties of the films have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature dependent resistivity (R-T), and DC magnetization measurements. The films which were deposited at 600 C were post-annealed in an atmosphere of a gas mixture of Ar (93%) and O2 (7%), at temperature ranging between 800 and 880 C. This resulted in films which exhibited a single phase of 2212 with a high crystallinity (FWHM ≈ 0.16) and texturing along the c-axis, perpendicular to the plane of the substrate. An optimum temperature of 860 C was found for the post-annealing thermal treatment. The critical temperature, TC, of the films was measured as 82 K and the critical current density, JC, was calculated as 3 × 107 A/cm2 for the film annealed at 860 C.