Özyüzer, Lütfi
Loading...
Profile URL
Name Variants
Ozyuzer, L
Ozyuzer, L.
Özyüzer, L
Özyüzer, L.
Ozyuzer, Lutfi
Ozyuzer, L.
Özyüzer, L
Özyüzer, L.
Ozyuzer, Lutfi
Job Title
Email Address
lutfiozyuzer@iyte.edu.tr
Main Affiliation
04.05. Department of Pyhsics
Status
Current Staff
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Sustainable Development Goals
1NO POVERTY
0
Research Products
2ZERO HUNGER
0
Research Products
3GOOD HEALTH AND WELL-BEING
0
Research Products
4QUALITY EDUCATION
0
Research Products
5GENDER EQUALITY
0
Research Products
6CLEAN WATER AND SANITATION
4
Research Products
7AFFORDABLE AND CLEAN ENERGY
26
Research Products
8DECENT WORK AND ECONOMIC GROWTH
5
Research Products
9INDUSTRY, INNOVATION AND INFRASTRUCTURE
29
Research Products
10REDUCED INEQUALITIES
0
Research Products
11SUSTAINABLE CITIES AND COMMUNITIES
0
Research Products
12RESPONSIBLE CONSUMPTION AND PRODUCTION
6
Research Products
13CLIMATE ACTION
14
Research Products
14LIFE BELOW WATER
1
Research Products
15LIFE ON LAND
0
Research Products
16PEACE, JUSTICE AND STRONG INSTITUTIONS
0
Research Products
17PARTNERSHIPS FOR THE GOALS
0
Research Products
Documents
127
Citations
3856
h-index
29
Documents
97
Citations
3410
Scholarly Output
147
Articles
83
Views / Downloads
353972/66154
Supervised MSc Theses
28
Supervised PhD Theses
4
WoS Citation Count
2929
Scopus Citation Count
2904
Patents
0
Projects
27
WoS Citations per Publication
19.93
Scopus Citations per Publication
19.76
Open Access Source
123
Supervised Theses
32
| Journal | Count |
|---|---|
| Physica C: Superconductivity and its Applications | 11 |
| IEEE Transactions on Applied Superconductivity | 7 |
| Vacuum | 7 |
| Physical Review B - Condensed Matter and Materials Physics | 6 |
| Thin Solid Films | 5 |
Current Page: 1 / 12
Scopus Quartile Distribution
Competency Cloud
147 results
Scholarly Output Search Results
Now showing 1 - 10 of 147
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.Master Thesis Anti-Reflective and Optical Transparent Coatings for Thin Film Solar Cells and Glasses(Izmir Institute of Technology, 2020) Kamolov, Shukrullo; Özyüzer, Lütfi; Özyüzer, LütfiAntireflective coatings in some implementation necessary for the decreasing surface reflection, but in some applications also for increasing transmittance. Incident radiation on the surface of the optical material is divided into transmitted, reflected, scattered, and absorbed proportions, and the proportion of current energy that deployed among them is defined by RI (refraction indices). Solar panels made from crystalline or polycrystalline silicon, but another type of solar panel is a thin-film solar panel. Thin-film technology has several advantages, such as low material consumption, which leads to cost savings to production, the ability to absorb diffused solar radiation, a relatively high efficiency (up to 20%), long service life (efficiency decreases by 10-15% of the initial efficiency). For all types of photovoltaic devices, energy loss is an important issue. Single-layer and two-layer antireflection coatings with a low refractive index, coated and uncoated (SiO2) thin-film with the sol-gel method were prepared and compared in terms of performance and continuity. The photocatalytic performance of (SiO2) thin films in 1, 2, 3, 4, 5 and 24 hours was defined with methylene blue dye solution (20 mL) under UV source and was illuminated by it. The I-V characteristics curve of solar cells for small and large area was learned and increasing efficiency was observed. Adhesion tests in this study was applied by tape tests on substrates of glass. As a result, the field tests of small and large area glasses coated solar panels were realized, the low reflectance and high efficiency were obtained.Article Citation - WoS: 7Citation - Scopus: 7Comparative Study of Annealing and Gold Dopant Effect on Dc Sputtered Vanadium Oxide Films for Bolometer Applications(Springer Verlag, 2017) Alaboz, Hakan; Demirhan, Yasemin; Yüce, Hürriyet; Aygün, Gülnur; Özyüzer, LütfiVanadium oxide (VOx) thin film has been widely used for IR detectors and it is one of the promising materials for THz detectors due to its high temperature coefficient of resistance (TCR) values. VOx films with proper TCR values have also high resistance and it restricts bolometer performance especially for uncooled bolometers. To overcome this problem, deposition at elevated temperatures or annealing approach has been accepted and used but gold co-deposition approach has been proposed recently. In this study, vanadium oxide films were fabricated on high resistivity silicon substrates by reactive direct current magnetron sputtering in different O2/Ar atmosphere at room temperature. We investigated influence of oxygen partial pressure during deposition process and fabricated VOx thin films with sufficient TCR values for bolometer applications. In order to decrease resistivity of the deposited films, post annealing and gold doping approaches were performed separately. Effect of both post annealing process and gold doping process on structural and electrical properties of VOx thin films deposited at room temperature were investigated and detailed comparison between these methods were presented. We obtained the best possible approach to obtain optimum conditions for the highly reproducible VOx thin films which have the best resistivity and suitable TCR value for bolometer applications.Article Citation - WoS: 42Citation - Scopus: 43Counterintuitive Consequence of Heating in Strongly-Driven Intrinsic Junctions of Bi2 Sr2 Cacu2 O 8+? Mesas(American Physical Society, 2010) Kurter, Cihan; Özyüzer, Lütfi; Proslier, T.; Zasadzinski, John F.; Hinks, David G.; Gray, Kenneth E.Anomalously high and sharp peaks in the conductance of intrinsic Josephson junctions in Bi2 Sr2 CaCu2 O 8+δ (Bi2212) mesas have been commonly interpreted as superconducting energy gaps but here we show they are a result of strong self-heating. This conclusion follows directly from a comparison to the equilibrium gap measured by tunneling in single break junctions on equivalent crystals. As the number of junctions in the mesa, N, and thus heating increase, the peak voltages decrease and the peak width abruptly sharpens for N≥12. Clearly these widely variable features vs N cannot all represent the equilibrium properties. Our data imply that the sharp peaks represent a transition to the normal state. That it occurs at the same dissipated power for N=12-30 strongly implicates heating as the cause. Although peak sharpening due to heating is counterintuitive, as tunneling spectra usually broaden at higher temperatures, a lateral temperature gradient, leading to coexistence of normal hot spots and superconductive regions, qualitatively explains the behavior. However, a more uniform temperature profile cannot be ruled out. As the peak's width and voltage in our shortest mesa (N=6) are more consistent with the break junction data, we propose a figure of merit for Bi2212 mesas, the relative conductance peak width, such that small values signal a crossover into the strong self-heating regime. © 2010 The American Physical Society.Master Thesis Indium Tin Oxide (ito) Coating on Cylindricalsurfaces: Electrical and Structural Characterization(Izmir Institute of Technology, 2015) Arslan, Halil; Aral, Gürcan; Özyüzer, Lütfi; Özyüzer, Lütfi; Aral, GürcanOptical transparent conductive oxides (TCOs) which were discovered in the first quarter of twentieth century, and which belong to the class of semiconductor elements, are the constituent of today’s and future technology thanks to the high optical transparency ( ≥ % 85) they have in the visible region (390- 700 nm), and to the low electrical resistivity they have (10-4 ohm.cm). One of the most common usage of optical transparent conductive oxides; which have a quite extensive application area from transistors to solar panels, from flexible screens to OLEDs; is the textile materials known as smart clothes. The use of TCOs in textile materials, generally occurs by means of electrochromic structures that have the feature of changing color. In the most general sense, electrochromic structures can be defined as the materials that change their colors, which they gain thanks to reduction and oxidation reactions under a low potential difference of 1.5 – 5V, as a transition from one color state to another or from colorless state to color state. Even though they differ according to their area of utilization, electrochromic structures are generally consisted of seven layers as; Surface / conductive thin film (TCO) / Electrolyte film / Ionic conductive layer / Opposite electrolyte film / Conductive thin film (TCO) / and Surface. Electrical conductor and optical transparent indium doped tin oxide (ITO) film that are of vital importance in electrochromic fiber structures, were deposited on the fiber surface along with the specially-designed magnetic sputter in order to coat the cylindrical surfaces within the scope of the thesis. Film deposition was repeated by replacing the ionizing gas (Ar) flow rate and the energy applied. While the structural characterization of thin films was carried out by means of optical microscope and scanning electron microscope (SEM), electrical characterization of deposited thin film, was carried out by a multi-meter (Ohm meter). In addition, the thickness of thin film that was magnified on the surface of the fiber, was calculated by SEM particularly, and also by different methods. As a result of the analyzes carried out, it was observed that ~ 40 sccm ionizing gas flow rate, 90 W applied energy, and 119 cm/min fiber feed rate increased the quality of the thin film acquired.Article Citation - WoS: 13Citation - Scopus: 13Fourcross Shaped Metamaterial Filters Fabricated From High Temperature Superconducting Ybco and Au Thin Films for Terahertz Waves(IOP Publishing Ltd., 2017) Demirhan, Yasemin; Alaboz, Hakan; Nebioğlu, Mehmet Ali; Mulla, B.; Akkaya, M.; Altan, Hakan; Sabah, Cumali; Özyüzer, LütfiIn this study, we present a new, unique fourcross shaped metamaterial terahertz (THz) filter fabricated from both gold thin films and YBa2Cu3O7-δ high Tc superconducting thin films. A commercial electromagnetic simulation software, CST Microwave Studio, is used to design and optimize the metamaterial filter structures. The proposed fourcross shaped rectangular filter structure consists of periodic metallic rings where strip lines are located at the sides of the ring. Fourcross metamaterial filters are fabricated by using e-beam lithography and ion beam exhing techniques. Terahertz time-domain spectroscopy measurements validated the design predictions for both the center frequencies and bandwidths of the resonances due to the fourcross structures. The resonance switching of the transmission spectra was investigated by lowering the temperature below the critical transition temperature. This resonance switching effect is not observed in filters made up of metals. This novel fourcross rectangular resonator with a temperature-dependent resonance behavior holds great potential for active, tunable and low loss THz devices for imaging, sensing, and detection applications.Article Citation - WoS: 8Citation - Scopus: 8Redistribution of the Density of States Due To Coulomb Interactions in La2-2x Sr1+2x Mn2 O7(American Physical Society, 2007) Mazur, Daniel; Gray, Kenneth E.; Zasadzinski, John F.; Özyüzer, Lütfi; Beloborodov, Igor S.; Zheng, H.; Mitchell, J. F.Tunneling data on La1.28 Sr1.72 Mn2 O7 crystals confirm Coulomb interaction effects through the E dependence of the density of states. Importantly, the data and analysis at high energy E show a pileup of states: most of the states removed from near the Fermi level are found between ∼40 and 130 meV, from which we infer the possibility of universal behavior. The agreement of our tunneling data with recent photoemission results further confirms our analysis.Article Citation - WoS: 6Citation - Scopus: 6Nanolitography Based on Electrospun and Etched Nanofibers(Elsevier, 2021) Noori, Aileen; Döğer, Hilal; Demirhan, Yasemin; Özdemir, Mehtap; Özyüzer, Lütfi; Aygün, Gülnur; Sağlam, ÖzgeIn this study, we propose a new type of nanolithography procedure to fabricate orderly patterned metallic nanostructures using the electrohydrodynamic method and the reactive ion etching process. The electrohydrodynamic process parameters were tuned so as to create patterning with precision, and fibers in nanoscale on silver-coated substrates. We also studied reactive ion etching with different durations on the well-patterned samples. The experiments show that applying a voltage of 400 V resulted in straight patterned fibers with a diameter of 208.7 ? 30.3 nm. The statistical analysis on scanning electron microscope (SEM) images showed a significant difference in the diameter of the fibers fabricated at 400 V compared to those at 500 V and 600 V. We also confirm that the etching process has no affect on the fiber diameter. Moreover, electron dispersive X-Ray spectrometer (EDX) results suggest that an etching duration of 7 min is sufficient to remove the silver coating that is not covered with the fibers, and protect the silver nanostructures underneath the fibers. Utilizing a lowcost nanolithography procedure, we obtain the orderly patterned silver nanostructures for possible integration into miniaturized devices.Master Thesis Reactive Ion Beam Etching and Characterization of High-Tc Superconductor Bi2212(Izmir Institute of Technology, 2009) Köseoğlu, Hasan; Özyüzer, LütfiThe lack of coherent, continuous and tunable compact solid-state sources of electromagnetic radiations at terahertz (THz) frequency range (0.3-30 THz) can be solved by high temperature superconductors (HTS) which are better candidates for generation of THz radiation. THz sources have potential application areas in materials characterization, biology, communication, medicine and security. The HTSs have large energy gap intervals which are available for radiations at THz frequency range, so recently, they were used as better converters from DC-voltage to high frequency radiation in junction technologies. Bi2Sr2CaCu2O8+. (Bi2212) HTS single crystals include natural superconductor-insulator-superconductor multi-junctions called intrinsic Josephson junctions. For generation of coherent continuous and powerful THz radiations, we have fabricated large and tall mesas on Ca rich Bi2212, although mesas with small planar and lateral dimensions were preferred in recent studies because of the heating effect. We have used underdoped Bi2212 to control the heating problem. By using the vacuum thermal evaporation, optical photolithography, magnetron sputtering and reactive ion beam etching techniques, the mesas with size of 40-100x300 um2 have been fabricated by using single layer mask (PR) and two different multilayer masks, which are Ta/PR and PR./Ta/PR. Their heights and lateral dimensions were analyzed by Atomic Force Microscopy, profilometer and SEM. We have investigated temperature dependence of c-axis resistivity and current-voltage (I-V) tunneling characteristics of under-doped Bi2212 which exhibit exponentially increases in resistivity from 300 K to Tc. The influences of heating effect were analyzed at temperature evolution of I-V measurements. Finally, bolometric detections of emission from long edges of mesas were done.Master Thesis Microstructural, Electrical and Mechanical Properties of Mgb2/Mg Metal Matrix Composites(Izmir Institute of Technology, 2004) Eğilmez, Mehmet; Özyüzer, LütfiThe recent discovery of superconducting MgB2 (2001) has risen a great interest because of its relatively high Tc (39 K). Furthermore, simple crystal structure, large coherence lengths, high critical current densities (Jc) and critical fields (Bc2), promise that MgB2 will be a good material for large-scale applications based on production of superconducting wires. However, MgB2 is not a stand-alone material to produce wires because of its brittle nature. The potential of MgB2/Mg composites for producing superconducting wires, is investigated. MgB2/Mg composites were prepared using metal matrix composite fabrication technique, which is an alternative to conventional wire fabrication methods such as powder in tube. MgB2 and Mg powders were mixed at different weight fractions and uniaxially pressed in a cylindrical dye under the pressure of 0.5 GPa and 1GPa for two hours at different temperatures in the air. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Dispersive X-Ray Spectroscopy (EDX) techniques were used for phase identification and microstructural studies. D.C resistivity measurements were carried on the pellet segments of the MgB2/Mg composites in the temperature range 20-300 K. Magnetization measurements were done on the composites using a vibrating sample magnetometer to characterize the magnetic properties of the samples. The effects of pressing temperature on the mechanical properties of MgB2/Mg composites were also investigated. For this purpose, compressive mechanical testing were performed to measure elastic modulus and strength at failure values of the composites. It was found that the relative weight fractions of Mg and the pressing temperature have some considerable effect on the electrical, magnetic, microstructural and the mechanical properties of the composites.