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Öğe A Step toward the Wet Surface Chemistry of Glycine and Alanine on Cu{110}: Destabilization and Decomposition in the Presence of Near-Ambient Water Vapor(AMER CHEMICAL SOC, 2011) Shavorskiy, Andrey; Aksoy, Funda; Grass, Michael E.; Liu, Zhi; Bluhm, Hendrik; Held, GeorgThe coadsorption of water with organic molecules under near-ambient pressure and temperature conditions opens up new reaction pathways on model catalyst surfaces that are not accessible in conventional ultrahigh-vacuum surface-science experiments. The surface chemistry of glycine and alanine at the water-exposed Cu{110} interface was studied in situ using ambient-pressure photoemission and X-ray absorption spectroscopy techniques. At water pressures above 10(-5) Torr a significant pressure-dependent decrease in the temperature for dissociative desorption was observed for both amino acids, accompanied by the appearance of a new CN intermediate, which is not observed for lower pressures. The most likely reaction mechanisms involve dehydrogenation induced by O and/or OH surface species resulting from the dissociative adsorption of water. The linear relationship between the inverse decomposition temperature and the logarithm of water pressure enables determination of the activation energy for the surface reaction, between 213 and 232 kJ/mol, and a prediction of the decomposition temperature at the solid-liquid interface by extrapolating toward the equilibrium vapor pressure. Such experiments near the equilibrium vapor pressure provide important information about elementary surface processes at the solid-liquid interface, which can be retrieved neither under ultrahigh vacuum conditions nor from interfaces immersed in a solution.Öğe In Situ Observation of Water Dissociation with Lattice Incorporation at FeO Particle Edges Using Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy(AMER CHEMICAL SOC, 2011) Deng, Xingyi; Lee, Junseok; Wang, Congjun; Matranga, Christopher; Aksoy, Funda; Liu, ZhiThe dissociation of H(2)O and formation of adsorbed hydroxyl groups, on FeO particles grown on Au(111) were identified with in situ,: X:ray photoelectron spectroscopy (XPS) at water pressures ranging from 3 x 10(-8) to 0.1 Torr. The facile dissociation of H(2)O takes place at FeO particle edges, and it was successfully observed in situ With atomically resolved scanning tunneling microscopy (STM). The in situ STM studies show that adsorbed hydroxyl groups were formed exclusively along the edges of the FeO particles with the 0 atom becoming directly incorporated into the oxide crystalline lattice The STM results are consistent with coordinatively unsaturated ferrous (CUF) sites along the FeO particle edge causing the observed reactivity with H(2)O. Our results also directly illustrate how structural defects and under.-coordinated sites participate in chemical reactions.Öğe In Situ Oxidation Study of Pt(110) and Its Interaction with CO(AMER CHEMICAL SOC, 2011) Butcher, Derek R.; Grass, Michael E.; Zeng, Zhenhua; Aksoy, Funda; Bluhm, Hendrik; Li, Wei-Xue; Liu, ZhiMany interesting structures have been observed for O(2)-exposed Pt(110). These structures, along with their stability and reactivity toward CO, provide insights into catalytic processes on open Pt surfaces, which have similarities to Pt nanoparticle catalysts. In this study, we present results from ambient-pressure X-ray photoelectron spectroscopy, high-pressure scanning tunneling microscopy, and density functional theory calculations. At low oxygen pressure, only chemisorbed oxygen is observed on the Pt(110) surface. At higher pressure (0.5 Torr of O(2)), nanometer-sized islands of multilayered alpha-PtO(2)-like surface oxide form along with chemisorbed oxygen. Both chemisorbed oxygen and the surface oxide are removed in the presence of CO, and the rate of disappearance of the surface oxide is dose to that of the chemisorbed oxygen at 270 K. The spectroscopic features of the surface oxide are similar to the oxide observed on Pt nanoparticles of a similar size, which provides us an extra incentive to revisit some single-crystal model catalyst surfaces under elevated pressure using in situ tools.Öğe Investigation of structural and optical properties of InP thin films developed by using spraying method(AMER INST PHYSICS, 2007) Aksoy, Funda; Kayah, Refik; Oeztas, Mustafa; Bedir, Metin; Cetin, SA; Hikmet, IStructural and optical properties of InP films developed with the solutions prepared with InCl3 and Cl2HPO4 salts having different rates by using spraying method have been investigated using the data obtained from UV spectrometer and XRD (x-ray difractometer). Band gap energy values of all samples obtained by using UV spectrometer are found in 1.60-1.85 eV range. It was observed that basic piks of all samples are in (200) plane and have a fee structure in the XRD analysis. In addition, grain size of the samples increases with the rate of indium included in samples and it is seen that the crystallization in surface structure tends to become more homogenity.Öğe Kimyasal püskürtme yöntemiyle elde edilen InP ince filmlerinin elektrik, optik ve yapısal özelliklerinin incelenmesi(Niğde Üniversitesi, 2005) Aksoy, Funda; Kayalı, RefikÖZET KİMYASAL PÜSKÜRTME YÖNTEMİYLE ELDE EDİLEN InP İNCE PİMLERİNİN ELEKTRİK, OPTİK VE YAPISAL ÖZELLİKLERİNİN İNCELENMESİ AKSOY, Funda Niğde Üniversitesi Fen Bilimleri Enstitüsü Fizik Anabilim Dalı Danışman : Prof. Dr. Refik KAYALI Temmuz 2005, 67 sayfa Değişik oranlarda alman InCl3 ve Na2HP04 ile hazırlanan eriyikler kullanılarak püskürtme yöntemi ile değişik taban sıcaklıklarında kuvars cam alttabanlar üzerine oluşturulan amorf InP ince filmlerinin elektriksel, optik ve yapısal özellikleri; dört nokta yöntemi, Hail mobilite deneyi, UV spektrometresi, XRD ve SEM gibi ölçüm yöntemleri ile incelendi. Dört nokta yöntemiyle, aynı alt taban sıcaklığında farklı oranlarda hazırlanan iki ince film örneğinin karanlıktaki elde edilen özdirenç değerleri 6.25xl04 ve 19.11xl04 Q-cm ve ışık allında elde edilen değerleri de 5.74xl04 ve 12.57xl04 Q-cm bulundu. Aynı örneklerin Hail mobiliteleri 1.04x1ü2 ve 38.58xl0"2 cm2/V-s olarak elde edildi, özdirenç ve Hail mobilite değerleri karşılaştırıldığında özdirençteki artışın Hail mobilitesinde azalışa neden olduğu görüldü. UV spektrometresi ölçüm sonuçlarından yararlanarak, farklı oranlarda ve alt taban sıcaklılarında hazırlanan InP ince film örnekleri için elde edilen enerji bant aralığı değerleri 1.60-1.85 eV arasında değişmektedir. Örneklerin yapısal özellikleri XRD ve SEM yöntemleriyle tespit edildi. XRD ve SEM ölçümü sonuçlarından tüm ince film örneklerinde homojen bir polikristalleşmenin olduğu, fakat kristalleşmenin farklı boyut ve şekillerde meydana geldiği görüldü. Bunun yanı sıra, ince film örneklerinin içerdiği indiyum oranının artmasıyla doku boyutlarının arttığı ve buna bağlı olarak yüzey yapısındaki kristalleşmenin homojenliğe doğru gittiği görüldü. Anahtar Sözcükler: MP, püskürtme yöntemi, elektrik ve optik özellikler, ince filmler mÖğe Temperature and Thickness Effects on Electrical Properties of InP Films Deposited by Spray Pyrolysis(IOP PUBLISHING LTD, 2009) Kayali, Refik; Ari, Mehmet; Oeztas, Mustafa; Bedir, Metin; Aksoy, FundaInP film samples are prepared by spray pyrolysis technique using aqueous solutions of InCl(3) and Na(2)HPO(4), which are atomized with compressed air as carrier gas onto glass substrates at 500 degrees C with different thicknesses of the films. The structural properties of the samples are determined by x-ray diffraction (XRD). It is found that the crystal structure of the InP films is polycrystalline hexagonal. The orientations of all the obtained films are along the c-axis perpendicular to the substrate. The electrical measurements of the samples are obtained by dc four-probe technique on rectangular-shape samples. The effects of temperature on the electrical properties of the InP films are studied in detail.Öğe The morphology and structural properties of InP thin films deposited by spray pyrolysis method(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Aksoy, Funda; Kayali, Refik; Oeztas, Mustafa; Bedir, MetinInP film samples were prepared by spray pyrolysis technique using aqueous solutions of InCl3 and Na2HPO4, which were atomized with compressed air as carrier gas onto glass substrates at 500 degrees C with different thicknesses of the films. The structural properties of the samples have been determined by using X-ray diffraction (XRD). It was found that the crystal structure of the InP films is polycrystalline hexagonal. The orientations for all the obtained films are along the e-axis perpendicular to the substrate. It is observed that the crystallite sizes of the films increase with the thickness of the film up to 616 rim. The changes observed in the morphology and structural phases related to the film thickness have been discussed in detail. (C) 2007 Elsevier Ltd. All rights reserved.
