Aygün, Gülnur
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Özyüzer Aygün, Gülnur
Aygun, G.
Aygün, G.
Aygun, Gulnur
Aygun Ozyuzer, Gulnur
Aygün Özyüzer, Gülnur
Ozyuzer Aygun, Gulnur
Ozyuzer, Gulnur Aygun
Özyüzer, Gülnur Aygün
Aygun, G.
Aygün, G.
Aygun, Gulnur
Aygun Ozyuzer, Gulnur
Aygün Özyüzer, Gülnur
Ozyuzer Aygun, Gulnur
Ozyuzer, Gulnur Aygun
Özyüzer, Gülnur Aygün
Job Title
Email Address
gulnuraygun@iyte.edu.tr
Main Affiliation
04.05. Department of Pyhsics
Status
Current Staff
ORCID ID
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Google Scholar ID
WoS Researcher ID
Sustainable Development Goals
1NO POVERTY
0
Research Products
2ZERO HUNGER
0
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3GOOD HEALTH AND WELL-BEING
0
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4QUALITY EDUCATION
0
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5GENDER EQUALITY
0
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6CLEAN WATER AND SANITATION
1
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7AFFORDABLE AND CLEAN ENERGY
17
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8DECENT WORK AND ECONOMIC GROWTH
3
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
15
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10REDUCED INEQUALITIES
0
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11SUSTAINABLE CITIES AND COMMUNITIES
0
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
4
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13CLIMATE ACTION
8
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14LIFE BELOW WATER
0
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15LIFE ON LAND
0
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
0
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17PARTNERSHIPS FOR THE GOALS
0
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Documents
53
Citations
1259
h-index
21
This researcher does not have a WoS ID.
Scholarly Output
69
Articles
45
Views / Downloads
218667/33988
Supervised MSc Theses
12
Supervised PhD Theses
4
WoS Citation Count
1134
Scopus Citation Count
1228
Patents
0
Projects
14
WoS Citations per Publication
16.43
Scopus Citations per Publication
17.80
Open Access Source
51
Supervised Theses
16
| Journal | Count |
|---|---|
| Thin Solid Films | 8 |
| Vacuum | 5 |
| Journal of Physics D: Applied Physics | 4 |
| Journal of Applied Physics | 4 |
| Applied Surface Science | 3 |
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Scopus Quartile Distribution
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69 results
Scholarly Output Search Results
Now showing 1 - 10 of 69
Article Citation - WoS: 14Citation - Scopus: 18Xps Study of Pulsed Nd:yag Laser Oxidized Si(Elsevier Ltd., 2006) Özyüzer, Gülnur Aygün; Aygün, Gülnur; Atanassova, Elenada A.; Kostov, K.; Turan, RaşitX-ray photoelectron spectra (XPS) of thin SiO2 layers grown by pulsed Nd:YAG laser at a substrate temperature of 748 K are presented. The peak decomposition technique combined with depth profiling is employed to identify the composition and chemical states of the film structure. It is established that the oxide is non-stoichiometric, and contains all oxidation states of Si in different amounts throughout the film. The interface Si/laser-grown oxide is not abrupt, and the coexistence of Si2O3 and Si2O suboxides in a relatively wide interfacial region is found. It is concluded that post-oxidation annealing is necessary in order to improve the microstructure of both oxide and near interface region.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.Master Thesis Properties of Thin Film Lixlaytio3 Electrolyte for All-Solid State Li-On Batteries(Izmir Institute of Technology, 2016) Gülen, Sena; Aygün, Gülnur; Aygün Özyüzer, GülnurOne of the requirements of daily life, the most preferred rechargeable batteries are Li-ion batteries because of high energy, long life cycle and eco-friendly properties. Having high energy density, no memory effect and slow energy losses, these batteries have applications in portable electronic devices, power source for space vehicles, electric cars etc. Furthermore, there is a strong interest in all solid-state rechargeable lithium-ion battery research, because these batteries will replace the conventional liquid electrolyte Li-ion batteries due to use of non-combustible inorganic solid electrolyte, which has high safety and reliability. While the bulk ionic conductivity of La0.5Li0.5TiO3 (LLTO) produced by solid-state reaction is 10-3 S/cm, the total ionic conductivity of LLTO is 10-5 S/cm. Another way to increase ionic property is to dope the solid electrolyte with transition metals. The substitution of transition metal leads to decrease of the lattice parameter because of reduced average ionic radius. This causes increase of Li-ion content and also ionic conductivity. In this study, initially pure and Al doped targets were fabricated by using solid-state reaction after that the available targets are placed to the sputtering gun. When the all optimizations of the system were completed, pure and Al doped LLTO thin films were deposited by RF (radio frequency) magnetron sputtering technique on ITO coated soda lime glass substrates. While the thin film was been deposited, the substrate was heated at approximately 220 oC. For ionic conductivity measurement of the Al doped LLTO electrolyte, small circular Al contact regions were created on Al doped LLTO thin films by thermal evaporation system. Afterword the impedance spectra of the sandwich structure in a frequency range of 1 Hz - 200 MHz was recorded by using probe station. Thickness, the crystal structure, optical transmission, chemical compositions, surfaces and porosity of the thin films are investigated by surface profilometer, XRD, UV-Visible Spectroscopy, XPS, and Raman Spectroscopy respectively.Master Thesis Co Gas Sensor Applications of Fe Doped Calix[4] Arene Molecules(Izmir Institute of Technology, 2013) Özbek, Cebrail; Aygün, Gülnur; Aygün Özyüzer, GülnurInvisible and odourless carbon monoxide (CO) is one of the most toxic gas for respiratory systems. Therefore, the concentration level of carbon monoxide in the environment is extremely vital. In this thesis study, Calixarene molecules have been synthesized and the carbon monoxide selectivity and sensitivity of bare and iron doped calixarene molecules were measured by quartz crystal microbalance QCM technique and interdigitated electrodes with 3 ï m spacing. Calixarenes are promising compounds for sensing studies due to the well-designed cyclic structure, easily derivatization at both p- position of phenolic ring (upper rim) and phenolic-O (lower rim) as well as having diversely cavities which are a straightforward platform to form complex with molecules and ions. Quartz Crystal Microbalance is a powerful technique for nano scale determining the sorption properties of materials. According to Sauerbrey relation, the mass change on quartz crystal electrode cause a certain shift in the resonant frequency of vibrating crystal oscillator. This shift can be monitored using QCM method. In this study, a computer controlled QCM measurement system was developed for toxic gas detection. Iron doped calixarene based sensors were fabricated using drop-casting method on an AT-cut QCM gold electrode and interdigitated gold electrodes. The sensitivity and reproducible detection performances of prepared calixarene-iron doped calixarene thin films were measured under exposure of varying carbon monoxide for nitrogen and dry air used as desorption gas, respectively. The analysis of carbon monoxide sensitivity of iron doped calixarene is a new study for literature. This thesis study will guide future studies on this topic.Article Citation - WoS: 18Citation - Scopus: 20Impact of Incorporated Oxygen Quantity on Optical, Structural and Dielectric Properties of Reactive Magnetron Sputter Grown High-? Hfo2/Hf Thin Film(Elsevier Ltd., 2014) Cantaş, Ayten; Aygün, Gülnur; Turan, RaşitHigh-κ hafnium-oxide thin films have been fabricated by radio frequency (rf) reactive magnetron sputtering technique. To avoid formation of an undesired interfacial suboxide layer between Si and high-κ film, prior to HfO2 deposition, a thin Hf buffer layer was deposited on p-type (1 0 0) Si substrate at room temperature. Effect of oxygen gas quantity in the O2/Ar gas mixture was studied for the optical and structural properties of grown HfO2 high-κ thin films. The grown thin oxide films were characterized optically using spectroscopic ellipsometer (SE) in detail. Crystal structure was studied by grazing incidence X-ray diffractometer (GIXRD) technique, while bonding structure was obtained by Fourier transform infrared spectroscopy (FTIR) analyses. In agreement with GIXRD and FTIR analyses, SE results show that any increment above ideal quantity of oxygen content in the gas mixture resulted in decrements in the refractive index and thickness of HfO2 dielectric film, while increments in SiO2 thickness. It is apparent from experimental results that oxygen to argon gas ratio needs to be smaller than 0.2 for a good film quality. The superior structural and optical properties for grown oxide film were obtained for O2/Ar gas ratio of about 0.05-0.1 combined with ∼30 W constant rf sputtering power. © 2014 Elsevier B.V. All rights reserved.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.Article Citation - WoS: 25Citation - Scopus: 26Structural and Optical Characteristics of Tantalum Oxide Grown by Pulsed Nd:yag Laser Oxidation(AVS Science and Technology Society, 2006) Atanassova, Elenada A.; Aygün, Gülnur; Turan, Raşit; Babeva, T.Tantalum pentoxide (Ta2 O5) thin films (20-50 nm) have been grown by 1064 nm Nd:YAG laser oxidation of Ta film deposited on Si. The chemical bonding, structure, and optical properties of the films have been studied by Fourier transform infrared spectroscopy, x-ray diffraction, and reflectance measurements at normal light incidence in the spectral range of 350-800 nm. The effect of the substrate temperature (250-400 °C) during oxidation and its optimization with respect to the used laser beam energy density (3.2-3.4 J cm2 per pulse) is discussed. It is established that the substrate temperature is a critical factor for the effectiveness of the oxidation process and can be used to control the composition and amorphous status of the films. The film density explored by refractive index is improved with increasing film thickness. The refractive index of the layers grown under the higher laser beam energy density and at substrate temperature of 350-400 °C was found to be close to the value of bulk Ta2 O5. The films are amorphous at substrate temperature below 350 °C and possessed an orthorhombic (Β- Ta2 O5) crystal structure at higher temperatures. The thinner layers crystallize at a little higher temperature.Article Citation - WoS: 10Citation - Scopus: 10In-Situ Spectroscopic Ellipsometry and Structural Study of Hfo2 Thin Films Deposited by Radio Frequency Magnetron Sputtering(American Institute of Physics, 2014) Cantaş, Ayten; Özyüzer, Gülnur Aygün; Basa, Deepak KumarWe have investigated the reduction of unwanted interfacial SiO2 layer at HfO2/Si interface brought about by the deposition of thin Hf metal buffer layer on Si substrate prior to the deposition of HfO2 thin films for possible direct contact between HfO2 thin film and Si substrate, necessary for the future generation devices based on high-κ HfO2 gate dielectrics. Reactive rf magnetron sputtering system along with the attached in-situ spectroscopic ellipsometry (SE) was used to predeposit Hf metal buffer layer as well as to grow HfO2 thin films and also to undertake the in-situ characterization of the high-κ HfO2 thin films deposited on n-type 〈100〉 crystalline silicon substrate. The formation of the unwanted interfacial SiO2 layer and its reduction due to the predeposited Hf metal buffer layer as well as the depth profiling and also structure of HfO2 thin films were investigated by in-situ SE, Fourier Transform Infrared spectroscopy, and Grazing Incidence X-ray Diffraction. The study demonstrates that the predeposited Hf metal buffer layer has played a crucial role in eliminating the formation of unwanted interfacial layer and that the deposited high-κ HfO2 thin films are crystalline although they were deposited at room temperature.Article Citation - WoS: 24Citation - Scopus: 23Photovoltaic Performance of Magnetron Sputtered Antimony Selenide Thin Film Solar Cells Buffered by Cadmium Sulfide and Cadmium Sulfide /Zinc Sulfide(Elsevier B.V., 2023) Cantas, A.; Gundogan, S.H.; Turkoglu, F.; Koseoglu, H.; Aygun, G.; Ozyuzer, L.Antimony selenide (Sb2Se3)-based thin-film solar cells have recently attracted worldwide attention as an abundant, low-cost, and efficient photovoltaic technology. The highest efficiencies recorded for Sb2Se3 solar cells have been obtained using cadmium sulfide (CdS) as a buffer layer. The Cd-included hybrid buffer layers could be one option to increase device efficiency through more effective usage of light. Therefore, in this work, the effect of single CdS and hybrid CdS/zinc sulfide (ZnS) buffer layers on the photovoltaic performance of Sb2Se3 thin-film solar cells has been investigated in detail. Sb2Se3 thin films have been deposited on molybdenum (Mo)-coated soda-lime glass (SLG) substrates by radio frequency magnetron sputtering technique followed by a post-heat treatment process. The morphological, and structural properties of Sb2Se3 thin films have been investigated by X-Ray Diffraction and Scanning Electron Microscopy. To compare the device performances of single CdS and hybrid CdS/ZnS buffered Sb2Se3 thin-film solar cells, SLG/Mo/Sb2Se3/CdS/ZnS/indium tin oxide (ITO) and SLG/Mo/Sb2Se3/CdS/ITO structures have been fabricated. The findings of this study have revealed a reduction in solar cells’ performance from η=3.93% for CdS buffer to η=0.13% for CdS/ZnS hybrid buffer. The change in the solar cell performance using the CdS/ZnS hybrid buffer has been discussed in detail. © 2023 Elsevier B.V.Article Citation - WoS: 15Citation - Scopus: 17Effect of Substrate Rotation Speed and Off-Center Deposition on the Structural, Optical, and Electrical Properties of Azo Thin Films Fabricated by Dc Magnetron Sputtering(American Institute of Physics, 2018) Türkoğlu, Fulya; Aygün, Gülnur; Köseoğlu, Hasan; Özdemir, Mehtap; Zeybek, S.; Özyüzer, Lütfi; Özdemir, Mehtap; Özyüzer, Gülnur Aygün; Özyüzer, LütfiIn this study, aluminum-doped zinc oxide (AZO) thin films were deposited by DC magnetron sputtering at room temperature. The distance between the substrate and target axis, and substrate rotation speed were varied to get high quality AZO thin films. The influences of these deposition parameters on the structural, optical, and electrical properties of the fabricated films were investigated by X-ray diffraction (XRD), Raman spectroscopy, spectrophotometry, and four-point probe techniques. The overall analysis revealed that both sample position and substrate rotation speed are effective in changing the optical, structural, and electrical properties of the AZO thin films. We further observed that stress in the films can be significantly reduced by off-center deposition and rotating the sample holder during the deposition. An average transmittance above 85% in the visible range and a resistivity of 2.02 × 10-3Ω cm were obtained for the AZO films.