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Title: Quantitative analysis of adsorbate structures on Ir{100}
Author: Johnson, Anna Karina
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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Quantitative low energy electron diffraction has been used to determine the surface structure of a range of adsorbates, from simple atomic species to more complex molecular adsorbates, on Ir{100}. Only the clean surface structures of Ir{100} have been studied by LEED, so firstly simple atomic adsorbates, oxygen and carbon, were studied to build up the knowledge base for this surface, before progressing onto more complex adsorbates. After determining the surface structures for oxygen and carbon, a simple molecular adsorbate, carbon monoxide, was studied, followed by a more complex molecular adsorbate, benzene. Adsorption behaviour on both the (1x5) and (1x1) surfaces of Ir{100} was considered. All of the adsorbates lift the (1x5) reconstruction, although only oxygen lifts it completely. On the (1x1) surface all the adsorbates form ordered structures, except benzene, which forms an ordered overlayer after thermal decomposition to benzyne. Oxygen adatoms are found to adsorb on bridge sites in a p(1x2) arrangement where rows of first layer iridium atoms pair up. In contrast, carbon is adsorbed on the four-fold hollow site with c(2x2) periodicity. Carbon monoxide also forms a c(2x2) overlayer but is adsorbed on the atop site: the molecule bonds through carbon with the C-O bond perpendicular to the surface. Formation of benzyne from benzene results in a c(2x4) LEED pattern. LEED analysis of this structure shows that the benzyne molecule is adsorbed on the bridge site and tilted 48° from the surface normal. This is the first full structure determination of adsorbed benzyne.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available