Nanocluster defects and their properties on TiO2(110) and (001) surfaces.

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dc.contributor.advisor Park, Kenneth Taesung, 1965- Yu, Nan-Hsin. 2012-08
dc.description.abstract TiO2(110) and (001) have been investigated by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). A nearly bulk-like (1 × 1) TiO2(110) was produced after cycles of Ar+ sputtering and surface annealing at moderate conditions. However, with an increasing number of preparation cycles, the partially reduced surface was then obtained. The surface was heterogeneous with the formation of dispersed nanometer-sized bright strands terminated with bright nanoclusters on the (1 × 1) terraces. They were identified as substoichiometric (TiOx, x < 2) and stoichiometric defects, respectively. Upon the adsorption of gold, the stoichiometric nanoclusters were observed to be the most active sites for the initial nucleation of Au and the subsequent formation of nanoparticles. The first principles calculations indicated that both geometric and electronic effects of the under-coordinated O atoms of the nanocluster with surface O atoms were responsible for exceptionally strong binding sites for Au nanoparticles. This atomistic model suggests a potentially active site for low temperature CO oxidation by Au nanoparticles. TiO2(001) under similar preparation conditions revealed the so-called latticework reconstruction: row-like linear structures running along [110] and [1-10] directions. Each row further consisted of bright spots separated by 6.5 Å. In some areas, the rows were separated by 13 Å consistent with the lattice domains of (2r2xr2)R45° observed by LEED. In other areas, the rows were distributed in a more random fashion. Thus various nearest neighbor distances and relative heights of the rows formed different microfacets. From the LEED and STM data, a stoichiometric nanocluster is proposed as the basic building blocks for the latticework reconstruction. It is modeled using six TiO2 units located at bulk-extended positions on TiO2(001) similar to those on TiO2(110). The single-step height clusters can further grow into a linear structure either along [110] or [1-10], exhibiting many structural traits experimentally observed. en_US
dc.publisher en
dc.rights Baylor University theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. Contact for inquiries about permission. en_US
dc.subject TiO2(110) en_US
dc.subject TiO2(001) en_US
dc.subject Nanocluster defect. en_US
dc.title Nanocluster defects and their properties on TiO2(110) and (001) surfaces. en_US
dc.type Thesis en_US Ph.D. en_US
dc.rights.accessrights Worldwide access en_US
dc.contributor.department Physics. en_US
dc.contributor.schools Baylor University. Dept. of Physics. en_US

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