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Article Citation - WoS: 39Citation - Scopus: 40Illumination and Voltage Effects on the Forward and Reverse Bias Current-Voltage (i-V) Characteristics in In/In2< Photodiodes(Springer, 2021) Yukselturk, Esra; Surucu, Ozge; Terlemezoglu, Makbule; Parlak, Mehmet; Altindal, SemsettinThe illumination and voltage effects on the I-V measurements of the fabricated In/In2S3/p-Si photodiode were investigated in dark and under various illumination intensities (20-100 mW/cm(2)) between +/- 2 V. Two linear regions in the forward-bias ln(I)-V plots were observed. The value of diode ideality factor (n) had an increasing trend with increasing illumination intensity while the barrier height (phi(Bo)) had a decreasing trend due to the increase of photocurrent. The photodiode properties were also investigated, and the value of linear-dynamic value range (LDR) was found to be 20.56 dB. The photoresponse (I-ph/I-dark), the photoresponsivity (R), and specific detectivity (D*) of the photodiode were calculated as a function of the illumination. The open-circuit voltage (V-oc) and short-current (I-sc) were found to be 0.36 V and 2.87 mA under 100 mW.cm(-2) illumination intensity, respectively. The possible conduction mechanisms (CMs) were investigated using the forward ln(I)-V and reverse ln(I)-V-0.5 plots. The energy-dependent surface states (N-ss) profile was extracted from the positive I-V data by considering voltage-dependent barrier height (BH) and ideality factor (n) in dark and illumination at 100 mW/cm(2).Article Citation - WoS: 9Citation - Scopus: 8Exploring the Optical Dynamics in the Ito/As2< Interfaces(Springer, 2019) Al Garni, S. E.; Qasrawi, A. F.In this work, the effects of indium tin oxide (ITO) substrates on the structural, compositional, optical dielectric and optical conduction properties of arsenic selenide thin films are investigated. The As2Se3 films which are prepared by the thermal deposition technique under vacuum pressure of 10(-5) mbar exhibit an induced crystallization process, improved stoichiometry, increased optical transmittance in the visible range of light and increased dielectric response in the infrared range of light upon replacement of glass substrates by ITO. The ITO/As2Se3 interfaces exhibit conduction and valence band offset values of 0.46 eV and 0.91 eV, respectively. The experimental optical conductivity spectra are theoretically reproduced with the help of the Drude-Lorentz approach for optical conduction. In accordance with this approach, owing to the improved crystallinity of the arsenic selenide, the deposition of As2Se3 onto ITO substrates increases the drift mobility value from similar to 17.6 cm(2)/Vs to 34.6 cm(2)/Vs. It also reduces the density of free carriers by one order of magnitude. The ITO/As2Se3/C heterojunction devices which are tested as band filters which may operate in the frequency domain of 0.01-3.0 GHz revealed low pass filter characteristics below 0.35 GHz and band pass filter characteristics in the remaining spectral range.Correction Correction: Evaluating Anterior Segment Stability and Corneal Endothelium After Prolene Gonioscopy Assisted Transluminal Trabeculotomy (GATT) in Open-Angle Glaucoma(Springer, 2025) Aribas, Yavuz Kemal; Aktas, Zeynep; Ertop, MestanArticle Citation - WoS: 14Citation - Scopus: 14Analysis of Temperature-Dependent Forward and Leakage Conduction Mechanisms in Organic Thin Film Heterojunction Diode With Fluorine-Based Pcbm Blend(Springer, 2020) Yildiz, D. E.; Gullu, H. H.; Toppare, L.; Cirpan, A.The forward and reversed biased current-voltage behaviors of the organic diode were detailed in a wide range of temperatures. In this diode, a donor-acceptor-conjugated copolymer system was constructed with poly((9,9-dioctylfluorene)-2,7-diyl-(2-dodecyl-benzo[1,2,3]triazole)) as a partner of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Two-order of magnitude rectification ratio was achieved, and the temperature-dependent values of saturation current, zero-bias barrier height, and ideality factor were extracted according to the thermionic emission model. The temperature responses of these diode parameters showed an existence of inhomogeneity in the barrier height formation. As a result, the observed non-ideal behavior was explained by Gaussian distribution of barrier height where low-barrier regions are effective in the forward biased conduction mechanism at low temperatures. Together with this analysis, series resistances were evaluated using Cheung's functions and also density of interface states were investigated. On the other hand, reverse biased current flow was found under the dominant effect of Poole-Frenkel effects associated with these interfacial traps. The reverse current conduction mechanism was detailed by calculating characteristic field-lowering coefficients and barrier height values in the emission process from the trapped state in the range of temperatures of interest.Article Citation - WoS: 1Outperformance of CaO-Incorporated Alumina-Supported Pd Catalysts in Methanol Decomposition(Springer, 2025) Eryildirim, Busra; Oktar, Nuray; Dogu, DorukThis study aimed to investigate the impact of CaO incorporation to alumina-supported Pd catalysts on the methanol decomposition reaction. For this purpose, mayenite, alumina and/or calcium oxide-supported Pd catalysts were synthesized. The synthesized catalysts were characterized by XRD, FTIR, Laser Raman spectroscopy, N2 adsorption-desorption, pyridine adsorbed DRIFTS, CO2-TPD, XPS, SEM-EDS, and ICP-OES techniques. Catalytic activity tests were carried out over a 6 h reaction period in the range of 100-400 degrees C. The results of the characterization and activity tests showed that the addition of CaO had significant effects on the physicochemical properties of the catalyst as well as on the catalytic activity. By adding CaO to the alumina support material, the acidity was reduced, thus reducing the selectivity for dimethyl ether (DME) formation, which is significantly high for the 1Pd@Al2O3 catalyst, and increasing the H2 and CO selectivity. The mayenite-supported catalyst (1Pd@SGM), which contains alumina and calcium oxide in its unique crystal structure, showed an excellent catalytic performance close to complete methanol conversion with DME selectivity below 1% at 400 degrees C. In the stability test carried out at 350 degrees C for 6 h with 1Pd@Al2O3, 1Pd@SGM, and 1Pd@48CaO@Al2O3 catalysts used in the temperature scan, it was concluded that all catalysts were stable and 1Pd@SGM catalyst showed higher catalytic activity than the others.Article Citation - Scopus: 3Complete Characterization of a Class of Permutation Trinomials in Characteristic Five(Springer, 2024) Grassl,M.; Özbudak,F.; Özkaya,B.; Temür,B.G.In this paper, we address an open problem posed by Bai and Xia in [2]. We study polynomials of the form f(x)=x4q+1+λ1x5q+λ2xq+4 over the finite field F5k, which are not quasi-multiplicative equivalent to any of the known permutation polynomials in the literature. We find necessary and sufficient conditions on λ1,λ2∈F5k so that f(x) is a permutation monomial, binomial, or trinomial of F52k. © The Author(s) 2024.Article Evaluating Anterior Segment Stability and Corneal Endothelium After Prolene Gonioscopy Assisted Transluminal Trabeculotomy (gatt) in Open-Angle Glaucoma(Springer, 2024) Aribas, Yavuz Kemal; Aktas, Zeynep; Ertop, MestanIntroduction This study investigates the short-term effects of prolene gonioscopy-assisted transluminal trabeculotomy (GATT) on anterior segment parameters and corneal endothelium in patients with open-angle glaucoma. Methods This retrospective study included 30 eyes from 30 patients who underwent GATT surgery. Demographic data, ophthalmological examination findings, and intraocular pressure (IOP) measurements using a Goldman applanation tonometer were recorded. Scheimpflug images were acquired at the pre-operative stage, as well as on the 1st day, 1st week, and 1st month postoperatively. Corneal endothelial cell counts were obtained via specular microscopy. Results The mean age of patients was 60.3 +/- 15.5 years. Anterior chamber depth and central corneal thickness increased on the 1st postoperative day (p:0.002, p < 0.001, respectively). Changes in anterior chamber depth values at the postoperative 1st week and 1st month compared to baseline were not statistically significant. Central corneal thickness decreased significantly at the 1st postoperative month compared to baseline (p:0.007). Corneal endothelial cell counts at the 1st month were comparable to baseline values (p:0.936). Conclusion Our findings reveal that prolene gonioscopy-assisted transluminal trabeculotomy induces temporary changes in anterior segment parameters but preserves corneal endothelial cell count within the first month, suggesting a promising profile for GATT in glaucoma management.Article Citation - WoS: 44Citation - Scopus: 52Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for Pem Fuel Cell(Springer, 2016) Devrim, Yilser; Albostan, AyhanThe aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70 degrees C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H-2/O-2 reactant gases as 0.925 W cm(2). The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm(2) at 0.6 V with H-2/O-2 and H-2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm(2) constant current density and 70 degrees C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.Article Citation - WoS: 17Citation - Scopus: 18A New Approximation in Determination of Vertical Displacement Behavior of a Concrete-Faced Rockfill Dam(Springer, 2011) Gurbuz, Ayhan; Gürbüz, Ayhan; Gürbüz, Ayhan; Department of Civil Engineering; Department of Civil EngineeringA new simplified method based on one-dimensional displacement theory and 2-D finite element (FE) analysis was developed to predict the vertical displacement behavior of a concrete-faced rockfill dam. The FE analyses were carried out at the end of construction (EOC) and the end of first filling of reservoir. The proposed method was calibrated by using continuously monitored vertical displacement of the dam's body to determine the mobilized modulus of elasticity of the rockfills at the EOC. The prediction capability of the method was demonstrated using field measurements against the findings from the 2-D FE analysis simulating characteristics of construction stages of the dam. The validity of the method was also examined on another membrane-faced rockfill dam by comparing the geodetic measurements of vertical displacement measurements of the dam's body with the calculated vertical displacements from 2-D FE analysis at the EOC.Article Citation - WoS: 2Citation - Scopus: 2Dielectric and Optoelectronic Properties of Inse/Cds Heterojunctions(Springer, 2018) Abusaa, M.; Qasrawi, A. F.; Shehada, Sufyan R.The effect of an InSe substrate on the structural, optical and dielectric properties of CdS/CdSe heterojunctions prepared by physical vapor deposition technique under vacuum pressure of 10(-8) bar are reported. The structural analysis carried out by x-ray diffraction revealed a strained type of growth of the CdS/CdSe heterojunction onto the InSe along the axis of the hexagonal lattice. The lattice mismatches and strained nature of the heterojunctions associated with the InSe participation causes a quantum confinement that results in a red shift in the energy band gap, enhanced near infrared (IR) light absorbability, and valence band offsets of 0.62eV and 0.53eV for the InSe/CdS and CdS/CdSe interfaces, respectively. In addition, a pronounced enhancement in the real part of the dielectric constant by 2.5 times is observed at 1.25eV. Furthermore, the Durde-Lorentz modeling of the optical conductivity of the CdS/CdSe and InSe/CdS/CdSe reveals significant increases in the drift mobility values from 43.8cm(2)/Vs at the CdS/CdSe interface to 100.0cm(2/)Vs upon replacement of glass by an amorphous InSe substrate. The other optical conduction parameters including the free carrier scattering time at the femtosecond level, the plasmon frequency and the free carrier density are also improved accordingly. The photocurrent illumination intensity dependence for the studied system showed that the presence of InSe increases the photocurrent values and changes the recombination mechanism from sublinear at the surface to trap-assisted recombination. The smart feature of the InSe/CdS/CdSe system is that the structurally controlled quantum confinement results in having mobile photocarriers arising from the enhanced absorbability and large dielectric response in the IR region.
