Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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Article Citation - WoS: 1Investigation of the Electrical Parameters of the Organic Diode Modified With 4-[(3 Benzoic Acid(Electrochemical Society, Inc., 2016) Havare, A. Kemal; Can, Mustafa; Yağmurcukardeş, Nesli; Yiğit, Mesude Zeliha; Aydın, Hasan; Okur, Salih; Demiç, Şerafettin; İçli, Sıddık4-[(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.Article Citation - WoS: 5Citation - Scopus: 4The Effect of Annealing Temperature on the Optical Properties of a Ruthenium Complex Thin Film(Elsevier Ltd., 2016) Ocakoğlu, Kasım; Okur, Salih; Aydın, Hasan; Emen, Fatih MehmetThe stability of the optical parameters of a ruthenium polypyridyl complex (Ru-PC K314) film under varying annealing temperatures between 278 K and 673 K was investigated. The ruthenium polypyridyl complex thin film was prepared on a quartz substrate by drop casting technique. The transmission of the film was recorded by using Ultraviolet/Visible/Near Infrared spectrophotometer and the optical band gap energy of the as-deposited film was determined around 2.20 eV. The optical parameters such as refractive index, extinction coefficient, and dielectric constant of the film were determined and the annealing effect on these parameters was investigated. The results show that Ru PC K314 film is quite stable up to 595 K, and the rate of the optical band gap energy change was found to be 5.23 × 10- 5 eV/K. Furthermore, the thermal analysis studies were carried out in the range 298-673 K. The Differential Thermal Analysis/Thermal Gravimmetry/Differantial Thermal Gravimmetry curves show that the decomposition is incomplete in the temperature range 298-673 K. Ru-PC K314 is thermally stable up to 387 K. The decomposition starts at 387 K with elimination of functional groups such as CO2, CO molecules and SO3H group was eliminated between 614 K and 666 K.Article Citation - WoS: 4Citation - Scopus: 4Effect of Aromatic Sams Molecules on Graphene/Silicon Schottky Diode Performance(Electrochemical Society, Inc., 2016) Yağmurcukardeş, Nesli; Aydın, Hasan; Can, Mustafa; Yanılmaz, Alper; Mermer, Ömer; Okur, Salih; Selamet, YusufAu/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 φB 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.Article Citation - WoS: 29Citation - Scopus: 31Electrical Properties of Sam-Modified Ito Surface Using Aromatic Small Molecules With Double Bond Carboxylic Acid Groups for Oled Applications(Elsevier Ltd., 2014) Can, Mustafa; Havare, Ali Kemal; Aydın, Hasan; Yağmurcukardeş, Nesli; Demir, Şerafettin; İçli, Sıddık; Okur, Salih5-[(3-Methylphenyl)(phenyl)amino]isophthalic acid (5-MePIFA) and 5-(diphenyl)amino]isophthalic acid (5-DPIFA) organic molecules were synthesized to form self-assembled monolayer on indium tin oxide (ITO) anode to enhance hole transport from ITO to organic hole transport layers such as TPD. The modified surface was characterized by scanning tunneling microscopy (STM). The change in the surface potential was measured by Kelvin probe force microscopy (KPFM). Our Kelvin probe force microscopy (KPFM) measurements showed that the surface potentials increased more than 100 mV with reference to bare indium tin-oxide. The results show that the threshold voltage on OLEDs with modified ITO is lowered significantly compared to OLEDs with unmodified ITO. The hole mobility of TPD has been estimated using space-charge-limited current measurements (SCLC).Article Citation - WoS: 3Citation - Scopus: 4Electrical Characterizations of Schottky Diodes on Ito Modified by Aromatic Sams(Polish Academy of Sciences, 2013) Havare, A. Kemal; Okur, Salih; Yağmurcukardeş, Nesli; Can, M.; Aydın, H.; Şeker, M.; Demiç, ŞerafettinIn order to understand the electronic properties of the organic Schottky diode, ITO/TPD/Al and ITO/SAM/ TPD/Al organic Schottky devices were fabricated to obtain currentffvoltage 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.Article Citation - WoS: 1Citation - Scopus: 1Improvement of Anode/Htl Interface Properties Using Self-Assembled Monolayer in Organic Electronic Devices(Polish Academy of Sciences, 2013) Yaman, M.; Yağmurcukardeş, Nesli; Havare, A. Kemal; Aydın, H.; Ocakoğlu, Kasım; Okur, SalihFabrication and characterization of highly effcient organic light-emitting diode with surface modification of indium tin oxide anodes by using self-assembled monolayer technique have been studied. Four different self-assembled molecules, K-28 ruthenium complex, octadecylamine hydrochloride, octadecyltrichlorosilane and mercaptohexdecanoic acid are used to modify ITO surface to improve the interface properties. Space charge limited currents measurements have been used to evaluate carrier mobility under steady state current. The results show that the surface properties such as the stability of ITO anode layer have significant effects on charge injection in organic light-emitting diode devices.Article Citation - WoS: 49Citation - Scopus: 51Voc Sensors Based on a Metal Oxide Nanofibrous Membrane/Qcm System Prepared by Electrospinning(Royal Society of Chemistry, 2014) Horzum Polat, Nesrin; Taşçıoğlu, Didem; Özbek, Cebrail; Okur, Salih; Demir, Mustafa MuammerWe report a simple synthetic route to fabricate crystalline ZnO and CeO2/ZnO nanofibrous mats and their sensing characteristics against volatile organic compounds (VOCs) such as benzene, propanol, ethanol, and dichloromethane. Precursor fibers were fabricated by electrospinning of poly(vinyl alcohol) and metal salt(s) at 2.5 kV cm-1 in aqueous solution. The fibers were directly deposited on the crystal surface of a quartz crystal microbalance (QCM). The crystal, which was coated by nanostructured PVA/metal precursor(s) fibers, was subjected to calcination in air at 500 °C for 5 h. The formation of an oxide based nanofiber mat was revealed by scanning electron microscopy and X-ray diffraction. Upon exposure of the nanofiber mats to the VOCs, the compounds adsorbed onto the surface of oxidic fibers. The physisorption of the compounds was confirmed by FTIR and QCM. Both systems showed sensitivity to the VOCs and they hold a broad promise particularly for sensing applications of volatile alcoholic compounds. The introduction of CeO2 into the ZnO structure reduced the sensitivity of ZnO most probably due to the decrement of oxygen vacancies.