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Title Surface-supported Ag islands stabilized by a quantum size effect: their interaction with small molecules relevant to ethylene epoxidation
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University/Publisher Iowa State University
Abstract Surface-supported Ag nanoparticles demonstrate quantum-size-effect (QSE) mediated growth behavior. 2-layer Ag islands are stabilized by QSE for Ag/Si(111)-7x7. O2 exposure on such system changes the Ag island height distribution: promoting 3-layer island growth at the expense of 1-, and 2-layer islands. This is an indication that oxygen adsorption changes QSE of Ag/Si(111)-7x7. Mild annealing following O2 exposure promotes growth of even higher islands (up to 9-layer high). Such trend indicates the instability of 3-layer islands with oxygen adsorption. Ethylene exposure on Ag/Si(111)-7x7 leads to protrusions on Ag islands and protrusive rims on island edges. But ethylene does not affect QSE of Ag/Si(111)-7x7 significantly. O2 exposure on Ag/NiAl(110) disrupts the relative stability of Ag bilayer (BL) islands stabilized by QSE. 1-BL island react with O2 to form indentations and protrusions. However, these features do not occur on 2-BL Ag islands. A possible explanation is that the adsorption energy of oxygen is much higher on 2-BL islands than on 1-BL islands.
Subjects/Keywords Ag/NiAl(110); Ag/Si(111)-7x7; chemisorption; ethylene epoxidation; oxygen; quantum size effect; Chemistry
Language en
Country of Publication us
Format application/pdf
Record ID oai:lib.dr.iastate.edu:etd-4345
Repository iastate
Date Indexed 2018-02-15

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…wavelength of electrons, and m is an integer. Ag/Si(111)-7x7 is a prototypical system where the QSE is well established [1,2,8,23,24]. After being deposited on the Si(111)-7x7 substrate at 150 K and subsequently annealed to room…

…stability of Ag islands. Studies of the interaction of oxygen with Ag/Si(111)-77 were previously reported [48,49], but these studies were performed at a low Ag coverage where 3D Ag islands were not formed. So the study of such a system…

…at a higher Ag coverage will be a subject of this work. The interaction of ethylene with Ag/Si(111)-77, as well as the interaction of oxygen with Ag/NiAl(110) are also important parts of this study. References [1] L…

…Catal.24 (2003), 433. [49] Z. Zhang, J. Jiao, Z. Jiang, D. Tan, Q. Fu, X. Bao, J. Vac. Sci. Technol. A. 26(2008), 1. 7 CHAPTER 2 EFFECT OF OXYGEN ON THE STABILITY OF AG ISLANDS ON SI(111)-77 A paper published…

…layer on Si(111)-77. Starting from a distribution dominated by islands that are 1 layer high (measured with respect to the wetting layer), coarsening in ultrahigh vacuum at room temperature leads to growth of 2layer islands at the…

…importance.3, 4 The optical properties of silver nanoparticles or films, in or on Si, are attracting attention for possible applications inphotovoltaics,5 fiber optics,6 and photonic band gap devices.7 In addition to its optical properties, silver is…

…attractive in such technologies because it is immiscible with silicon, a feature that is unusual among transition metals. The goal of the present work is to determine the effect of oxygen on the stability of Ag islands supported on Si(111), and…

…specifically whether Ag islands on Si(111) react differently to oxygen exposure, depending on their height. For Ag on Si(111)-77, it is believed that a quantum size effect (QSE) preferentially stabilizes Ag islands that are two…

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