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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 Electrical Characterizations of Schottky Diodes on ITO Modified by Aromatic SAMs(Polish Acad Sciences Inst Physics, 2013) Havare, A. K.; Okur, S.; Yagmurcukardes, N. T.; Can, M.; Aydin, H.; Seker, M.; Demic, S.In order to understand the electronic properties of the organic Schottky diode, ITO/TPD/Aland ITO/SAM/TPD/Al organic Schottky devices were fabricated to obtain current voltage characteristics. From the slopes and y-axis intercepts of the plots, the values of the ideality factor, barrier heights of the ITO/SAM/TPD/Al diode were determined as 2.03 and 0.56 eV, respectively. The surface characterizations of modified and unmodified ITO were performed via atomic force microscopy. DOT: 10.12693/APhysPolA.123.456Öğe Electrical Characterizations of Schottky Diodes on ITO Modified by Aromatic SAMs(Polish Acad Sciences Inst Physics, 2013) Havare, A. K.; Okur, S.; Yagmurcukardes, N. T.; Can, M.; Aydin, H.; Seker, M.; Demic, S.In order to understand the electronic properties of the organic Schottky diode, ITO/TPD/Aland ITO/SAM/TPD/Al organic Schottky devices were fabricated to obtain current voltage characteristics. From the slopes and y-axis intercepts of the plots, the values of the ideality factor, barrier heights of the ITO/SAM/TPD/Al diode were determined as 2.03 and 0.56 eV, respectively. The surface characterizations of modified and unmodified ITO were performed via atomic force microscopy. DOT: 10.12693/APhysPolA.123.456Öğe 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 Humidity sensing properties of ZnO nanoparticles synthesized by sol-gel process(Elsevier Science Sa, 2010) Erol, A.; Okur, S.; Comba, B.; Mermer, Oe; Arikan, M. C.ZnO nanoparticles have been synthesized by the sol-gel method with approximately 10 nm diameter and the humidity adsorption and desorption kinetics of ZnO nanoparticles were investigated by quartz crystal microbalance (QCM) technique. The morphology and crystal structure of the ZnO nanoparticles have been characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The roughness of the surface has been investigated using atomic force microscope (AFM). The dynamic Langmuir adsorption model was used to determine the kinetic parameters such as adsorption and desorption rates and Gibbs free energy under relative humidity between 45% and 88%. The relative sensitivity of the ZnO nanoparticles-based humidity sensor was determined by electrical resistance measurements. Our reproducible experimental results show that ZnO nanoparticles have a great potential for humidity sensing applications at room temperature operations. (C) 2009 Elsevier B.V. All rights reserved.Öğe Investigation of the Electrical Parameters of the Organic Diode Modified with 4-[(3-Methylphenyl)(phenyl)amino] Benzoic Acid(Electrochemical Soc Inc, 2016) Havare, A. Kemal; Can, M.; Yagmurcukardes, N.; Yigit, M. Z.; Aydin, H.; Okur, S.; Demic, S.; Icli, S.4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) self-assembled monolayer (SAM) molecules as hole injection is formed on p and n type Si and on indium-tin oxide (ITO) electrodes to investigate the effect on the electrical parameters of hole only organic device. The hole mobility improvement of organic device was attributed to an intermediate energy level formed between hole transport materials (HTL) (N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine -NPB) and ITO when forming an ultrathin MPPBA layer, leading to increase of carrier mobility of the device. Space charge limited current (SCLC) technique is used to estimate the mobility of the NPB formed at the interface metal/organic Ohmic contact. The hole mobility of ITO/NPB/Al and ITO/MPPBA/NPB/Al devices were obtained as 1.80 x 10(-6) and 1.76 x 10(-3) cm(2)/Vs, at 1350 E (V/cm)(1/2) applied electric field, respectively. SAM modified devices has lower barrier height values. The electronic characteristic parameters of the ITO/(with or without MPPBA)/NPB/Al, Au/n-Si(or p-Si)/(with or without MPPBA)/Au contacts were calculated using current-voltage (I-V) measurements by Schottky type carrier injection. (C) The Author(s) 2016. Published by ECS.Öğe Structural and Vibrational Spectroscopy Investigation of the 5-[(diphenyl) amino] Isophthalic Acid Molecule(Amer Inst Physics, 2014) Kurt, M.; Sas, E. Babur; Can, M.; Okur, S.; Icli, S.; Demic, S.; Simos, TE; Kalogiratou, Z; Monovasilis, TThe molecular structure and vibrations of 5-(diphenyl) amino] isophthalic acid (DPIFA) were investigated by different spectroscopic techniques (such as infrared and Raman). FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. HOMO-LUMO analyses were performed. The theoretical calculations for the molecular structure and spectroscopic studies were performed with DFT (B3LYP) and 6-311G (d,p) basis set calculations using the Gaussian 09 program. After optimizing the geometry of the molecule, vibration wavenumbers and fundamental vibrations wavenumbers were assigned on the basis of the potential energy distribution (PED) of the vibrational modes calculated with VEDA 4 program. The results of theoretical calculations for the spectra of the title compound were compared with the observed spectra.Öğe Structural investigation of a self-assembled monolayer material 5-[(3-methylphenyl) (phenyl) amino] isophthalic acid for organic light-emitting devices(Pergamon-Elsevier Science Ltd, 2014) Sas, E. Babur; Kurt, M.; Can, M.; Okur, S.; Icli, S.; Demic, S.The molecular structure and vibrations of 5-[(3-methylphenyl) (phenyl) amino] isophthalic acid (MePIFA) were investigated by infrared and Raman spectroscopies, UV-Vis, H-1 and C-13 NMR spectroscopic techniques and NBO analysis. FT-IR, FT-Raman and dispersive Raman spectra were recorded in the solid phase. H-1 and C-13 NMR spectra and UV-Vis spectrum were recorded in DMSO solution. HOMO-LUMO analysis and molecular electrostatic potential (MEP) analysis were performed. The theoretical calculations for the molecular structure and spectroscopies were performed with DFT (B3LYP) and 6-311G(d,p) basis set calculations using the Gaussian 09 program. After the geometry of the molecule was optimized, vibration wavenumbers and fundamental vibration wavenumbers were assigned on the basis of the potential energy distribution (PED) of the vibrational modes calculated with VEDA 4 program. The total (TDOS), partial (PDOS) density of state and overlap population density of state (OPDOS) diagrams analysis were made using GaussSum 2.2 program. The results of theoretical calculations for the spectra of the title compound were compared with the observed spectra. (C) 2014 Elsevier B.V. All rights reserved.Öğe Synthesis and Raman spectroscopic investigation of a new self-assembly monolayer material 4-[N-phenyl-N-(3-methylphenyl)-amino]-benzoic acid for organic light-emitting devices(Wiley-Blackwell, 2011) Kurt, M.; Okur, S.; Demic, S.; Karpagam, J.; Sundaraganesan, N.We have synthesized 4-[N-phenyl-N-(3-methylphenyl)-amino]-benzoic acid (4-[PBA]) and investigated its molecular vibrations by infrared and Raman spectroscopies as well as by calculations based on the density functional theory (DFT) approach. The Fourier transform (FT) Raman, dispersive Raman and FT-IR spectra of 4-[PBA] were recorded in the solid phase. We analyzed the optimized geometric structure and energies of 4-[PBA] in the ground state. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was studied using natural bond orbital analysis. The results show that change in electron density in the sigma* and pi* antibonding orbitals and E-2 energies confirm the occurrence of intramolecular charge transfer within the molecule. Theoretical calculations were performed at the DFT level using the Gaussian 09 program. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution. The good agreement between the experimental and theoretical spectra allowed positive assignment of the observed vibrational absorption bands. Finally, the calculation results were applied to simulate the Raman and IR spectra of the title compound, which show agreement with the observed spectra. Copyright (C) 2011 John Wiley & Sons, Ltd.Öğe Synthesis and spectroscopic characterization on 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid: A DFT approach(Pergamon-Elsevier Science Ltd, 2016) Kurt, M.; Sas, E. Babur; Can, M.; Okur, S.; Icli, S.; Demic, S.; Karabacak, M.; Jayavarthanan, T.; Sundaraganesan, N.A complete structural and vibrational analysis of the 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid (TPBA), was carried out by ab initio calculations, at the density functional theory (DFT) method. Molecular geometry, vibrational wavenumbers and gauge including atomic orbital (CIAO) C-13 NMR and H-1 NMR chemical shift values of (TPBA), in the ground state have been calculated by using ab initio density functional theory (DFT/B3LYP) method with 6-311G(d,p) as basis set for the first time. Comparison of the observed fundamental vibrational modes of (TPBA) and calculated results by DFT/B3LYP method indicates that B3LYP level of theory giving yield good results for quantum chemical studies. Vibrational wavenumbers obtained by the DFT/B3LYP method are in good agreement with the experimental data. The study was complemented with a natural bond orbital (NBO) analysis, to evaluate the significance of hyperconjugative interactions and electrostatic effects on such molecular structure. By using TD-DFF method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFF method and the experimental one is determined. In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals analysis and thermodynamic properties of TPBA were investigated using theoretical calculations. (C) 2015 Elsevier B.V. All rights reserved.
