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Öğe The Comparison of the Novel Co-adsorbent Molecules' Effects on the DSSC's Efficiency(Ieee, 2016) Boz, M.; Yarici, I.; Can, M.; Mermer, O.; Pogrebnjak, ADIn this paper, the effect of co-adsorbed molecules used in Dye Sensitized Solar Cell (DSSC) on the performance parameters have been investigated. The aim of using these molecules is to prevent agglomeration during the soaking process of TiO2 covered electrodes. In order to understand the effect of the co-adsorbed molecules, typical DSSC devices with and without co-adsorbers were fabricated.Öğe Effect of Aromatic SAMs Molecules on Graphene/Silicon Schottky Diode Performance(Electrochemical Soc Inc, 2016) Yagmurcukardes, N.; Aydin, H.; Can, M.; Yanilmaz, A.; Mermer, O.; Okur, S.; Selamet, Y.Au/n-Si/Graphene/Au Schottky diodes were fabricated by transferring atmospheric pressure chemical vapor deposited (APCVD) graphene on silicon substrates. Graphene/n-Si interface properties were improved by using 5-[(3-methylphenyl)(phenyl) amino] isophthalic acid (MePIFA) and 5-(diphenyl) amino] isophthalic acid (DPIFA) aromatic self-assembled monolayer (SAM) molecules. The surface morphologies of modified and non-modified films were investigated by atomic force microscopy and scanning electron microscopy. The surface potential characteristics were obtained by Kelvin-probe force microscopy and found as 0.158 V, 0.188 V and 0,383 V as a result of SAMs modification. The ideality factors of n-Si/Graphene, n-Si/MePIFA/Graphene and n-Si/DPIFA/Graphene diodes were found as 1.07, 1.13 and 1.15, respectively. Due to the chain length of aromatic organic MePIFA and DPIFA molecules, also the barrier height phi(B) values of the devices were decreased. While the barrier height of n-Si/Graphene diode was obtained as 0.931 eV, n-Si/MePIFA/Graphene and n-Si/DPIFA/Graphene diodes have barrier height of 0.820 and 0.720 eV, respectively. (C) 2016 The Electrochemical Society. All rights reserved.Öğe Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes(Elsevier Science Bv, 2018) Aydin, H.; Bacaksiz, C.; Yagmurcukardes, N.; Karakaya, C.; Mermer, O.; Can, M.; Senger, R. T.; Sahin, H.; Selamet, Y.We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4"bis(diphenylamino)-1, 1':3"-terpheny1-5' carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-y1-1,1':3'1'-terpheny1-5' carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current-voltage (I-V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)-V dependences were determined as 2.13,1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as n-n interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode. (C) 2017 Elsevier B.V. All rights reserved.Öğe Gas Sensing Properties of Carbon Nanotubes Modified with Calixarene Molecules Measured by QCM Techniques(Polish Acad Sciences Inst Physics, 2012) Mermer, O.; Okur, S.; Sumer, F.; Ozbek, C.; Sayin, S.; Yilmaz, M.This study focuses on the characterization and optimization of calixarene modified carbon nanotube thin films for gas detection. Calixarene molecules were synthesized individually by considering their functional groups to attract the gas. Calixarene modified carbon nanotube based sensors were fabricated using drop-casting method on a quartz crystal microbalance gold electrode. Carbon monoxide, carbondioxide, oxygen and dry air were used as active gases for adsorption process, while high-purity nitrogen gas was used for desorption process. The selectivity and sensitivity of calixarene modified carbon nanotube are investigated in detail. Our experimental results show that functional calixarene modified carbon nanotube coated quartz crystal microbalance sensors are very sensitive and selective to gas of CO2 at room temperature operation.Öğe Optical and microstructural properties of pure and Ru doped SnO2 semiconducting thin films(Natl Inst Optoelectronics, 2014) Mermer, O.; Sozbilen, H.Pure and ruthenium (Ru) doped nanostructure SnO2 (Ru-SnO2) semiconductor films were prepared by sot-gel technique on glass substrates. The effect of Ru incorporation on microstructure and optical properties of SnO2 films was investigated. Crystalline structure, orientations, morphological, optical properties of the films were investigated by using XRD, SEM, AFM, VEECO profilometer, and UV spectrophotometer, respectively. The optical band gap, refractive index, extinction coefficient and dielectric constants were calculated by using transmittance and reflectance spectrum of the films. The obtained structural data indicated that all the films possess polycrystalline structure with tetragonal rutile SnO2 and Ru incorporation conducts to significant changes in the microstructure of the SnO2 films. In addition to these, the highest average optical transmittance value was obtained in the visible region for pure SnO2 film. It was found that optical band gap of film was decreased with the increase in Ru doping, and absorption edge shifted to higher wavelengths with incorporation of Ru.Öğe Preparation of a Ni-Mo-P-PCTFE nanocomposite coating and evaluation of its nano-tribological, mechanical and electrochemical performance(Royal Soc Chemistry, 2016) Khameneh-asl, S.; Farzaneh, A.; Teymourinia, H.; Mermer, O.; Hosseini, M. G.In this study, the tribological, mechanical and electrochemical performances of electrodeposited nickel- molybdenum- phosphorus (Ni-Mo-P) coating containing polychlorotrifluoroethylene (PCTFE) nanoparticles were investigated. The nanocomposite coatings were deposited from potassium sodium tartrate containing electrolytes at four different concentrations of PCTFE (0, 4, 8 and 20 g L-1). The surface morphology, chemical and phase compositions of the Ni-Mo-P/PCTFE coatings were investigated using field-emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX) and X-ray Diffractometry (XRD), respectively. Corrosion behaviour of the coatings was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Atomic force microscopy (AFM) was used to investigate the tribological properties of the surfaces and in addition, their water-repellency was determined. The results show that there is a significant enhancement in corrosion resistance with the incorporation of PCTFE particles into the Ni-Mo-P matrix. It was also observed that the addition of PCTFE in the Ni-Mo-P alloy matrix has resulted in a smoother surface with a low friction coefficient and excellent water repellency.Öğe PRODUCTION AND DEVELOPMENT OF MONOCLINIC YTTRIUM TANTALATE (M '-YTaO4) X-RAY PHOSPHOR VIA SOL-GEL TECHNIQUE(Technical Univ Cluj-Napoca, 2014) Yildirim, S.; Demirci, S.; Mermer, O.; Toparli, M.; Alicikus, L. Zumre Alican; Akman, F.; Celik, E.; Popescu, DMonoclinic yttrium tantalate (M'-YTaO4) are efficient X-ray phosphor used in X-ray medical imaging, in which these phosphor are used in films/screen cassettes, and also in electronic detector systems such as computed radiography, computed tomography and fluoroscopy. Performances of these phosphor are related to composition, crystalline structure, surface properties and luminescence properties of films. In this study, M'-YTaO4 films were synthesized by five steps sol-gel spin coating route on single crystal silicon substrate. And then these films were dried at 120 degrees C and were sintered at 1200 degrees C for 4 hours and slowly cooled to room temperature. The obtained films were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and differential thermal analysis (DTA). After sintering, monoclinic M'-YTaO4 phase was obtained.
