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HCl nanoscience at copper and copper/gold alloy surfaces

Altass, Hatem 2013. HCl nanoscience at copper and copper/gold alloy surfaces. PhD Thesis, Cardiff University.
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Abstract The reaction of HCl with clean, Cu(100) and (111), and Au/ Cu(100) surfaces was investigated using x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) under ultra high vacuum (UHV) conditions. Exposure of the Cu(100) and (111) samples to HCl at room temperature leads to the formation of a saturated copper chloride monolayer. In the case of Cu(100), the saturated coverage was half monolayer corresponding to a c(2x2)-Cl reconstruction (half monolayer is 7.25x1014 cm-2) while for Cu(111) it was one third monolayer consistent with the reconstruction of (√3x√3)R30o (one third monolayer 5.9x1014 cm-2). The interaction of HCl with preoxidised Cu(100) and (111) showed different behaviour from those of clean copper surface depending on the way of interaction of oxygen with copper surface. Interaction of HCl with peroxidised Cu(111) at saturation oxygen coverage leads to the adsorption of chlorine on top of the copper surface with one third coverage. In contrast, presence of oxygen on Cu(100) surface at saturation coverage or less leads to adsorb chlorine but with an excess in chlorine concentration (more than the expected c(2x2) coverage). Oxidized Cu(100) and (111) surface at elevated temperature leads to the formation multi oxide layer. The two oxide surfaces („‟44‟‟ and „‟29‟‟) observed at the Cu(111) depend on the temperature of the substrate at the time of oxidation. The (√2x2√2)R45o structure was observed on the Cu(100) surface on heating which is the same structure formed at saturation coverage at room temperature. Interaction of HCl with Cu(100) and (111) surfaces covered by multilayers of oxide lead to adsorption of chlorine on top of the copper surface with a coverage more than more than the saturation coverage. Interaction of HCl with Au/Cu(100) showed two different behaviour depending on the gold coverage. Au/Cu(100) alloy formed at half monolayer of gold coverage, forming c(2x2) structure. Exposure of the Au/Cu(100) alloy at half monolayer of gold coverage to HCl leads to the formation of c(2x2)-Cl structure with saturation coverage of half monolayer in similar manner of interaction of HCl with the clean cu(100) surface. Interaction of HCl with Au/Cu(100) surface at gold coverage more than half monolayer leads to a dealloying of the gold from the copper surface and forming the Au(111) surface. Cu-Cl formed underneath the Au(111) surface with excess of chlorine concentration.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:24

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