Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 12Citation - Scopus: 12Modification of Metal/Semiconductor Junctions by Self-Assembled Monolayer Organic Films(Elsevier Ltd., 2009) Yakuphanoğlu, Fahrettin; Okur, Salih; Özgener, HüseyinTwo new metal/molecule/semiconductor contacts, Au/n-Si/TDA/Au and Au/p-Si/ODM/Au, were fabricated to understand effect of organic compounds, tridecylamine and octadecylmercaptan self-assembled monolayer (SAM) films, on electrical charge transport properties of the metal/semiconductor junctions. The morphology of the organic monolayers deposited on Si substrates was investigated by atomic force microscopy. The molecular coverage of ODM deposited on p-Si is poorer than that of TDA on n-Si substrate. The ideality factors of the p-Si/ODM and n-Si/TDA diodes were found to be 1.66 and 1.48, respectively. The electrical results show that the tridecylamine monolayer passivated junction has a lower ideality factor. The ideality factor indicates clear dependence on two different type functional groups R-SH (Thiol) and R-NH2 (Amin) groups and it increases with different functional groups of organic molecule. The barrier height φb value of the n-Si/TDA diode is smaller than that of p-Si/ODM diode, as a result of chain length of the SAM organic molecules. The interface state density Dit values of the diodes were determined using conductance technique. The n-Si/TDA diode has the smaller interface state density according to p-Si/ODM diode. We have evaluated that the organic molecules control the electronic parameters of metal/semiconductor diodes and thus, organic modification helps to get one step closer towards to new organic assisted silicon based microelectronic 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.Article Citation - WoS: 74Humidity Sensing Properties of Zno-Based Fibers by Electrospinning(Elsevier Ltd., 2011) Horzum Polat, Nesrin; Taşçıoğlu, Didem; Okur, Salih; Demir, Mustafa MuammerZinc oxide (ZnO) based fibers with a diameter of 80-100 nm were prepared by electrospinning. Polyvinyl alcohol (PVA) and zinc acetate dihydrate were dissolved in water and the polymer/salt solution was electrospun at 2.5 kV cm-1. The resulting electrospun fibers were subjected to calcination at 500 °C for 2 h to obtain ZnO-based fibers. Humidity sensing properties of the fiber mats were investigated by quartz crystal microbalance (QCM) method and electrical measurements. The adsorption kinetics under constant relative humidity (RH) between 10% and 90% were explained using Langmuir adsorption model. Results of the measurements showed that ZnO-based fibers were found to be promising candidate for humidity sensing applications at room temperature.