Date of Award
1992
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
The interactions of O{dollar}\sb2{dollar} and water with Al(100) have been studied by Nuclear Reaction Analysis (NRA), Thermal Desorption Spectroscopy (TDS), measurement of the work function ({dollar}\Delta\phi{dollar}), Photoelectron Spectroscopy (PES) and Fourier Transform InfraRed-Reflection Absorption Spectroscopy (FTIR-RAS). The major findings of this study are: The {dollar}\sp{lcub}18{rcub}{dollar}O(p,{dollar}\alpha)\sp{lcub}15{rcub}{dollar}N nuclear reaction is a useful alternative for determining absolute oxygen coverages by NRA. The absolute coverage of oxygen on Ni(100) at 300 K as a function of {dollar}\sp{lcub}18{rcub}{dollar}O{dollar}\sb2{dollar} exposure has been measured; the coverage of 2.45 {dollar}\pm{dollar} 0.10 ML (1 monolayer (ML) on Ni(100) = 1.61 {dollar}\times{dollar} 10{dollar}\sp{lcub}15{rcub}{dollar} particles cm{dollar}\sp{lcub}-2{rcub}{dollar}) at saturation corresponds to 3-3.4 layers of NiO.;For the O{dollar}\sb2{dollar}-Al(100) interaction at 300 K, {dollar}\sim{dollar}0.35 ML (1 ML on Al(100) = 1.22 {dollar}\times{dollar} 10{dollar}\sp{lcub}15{rcub}{dollar} particles cm{dollar}\sp{lcub}-2{rcub}{dollar}) can exist within the plane of the surface at four-fold hollows. There is some evidence for chemisorbed oxygen at bridge sites for adsorption at 100 K. The formation of amorphous alumina is signified by a broad peak in the Al 2p core level PES spectrum, exhibiting a chemical shift (CS) of 2.5 to 2.7 eV; the value depends on the extent of oxidation. The peak with a CS of 1.4 eV is associated with the metal-oxide interface, and not chemisorbed oxygen. The saturation coverage of oxygen is between 1.7 and 2.1 ML (depending on the crystal temperature and the method of exposure), indicating that the surface passivates when slightly more than the first layer of Al atoms have reacted.;Water adsorption on Al(100) at 100 K is completely molecular. Non-hydrogen bonded groups at the surface of ice have been identified by FTIR-RAS. A macroscopic dipole, likely due to defects, is observed in the {dollar}\Delta\phi{dollar} during the formation of water multi-layers (ice). Between 150 and 220 K, 1 ML of adsorbed water dissociates to form 1 Ml of hydroxyl groups. Heating multi-layers of adsorbed water ({dollar}>\sim{dollar}2.5 ML) to the same temperature produces 1 ML of hydroxyls and 1.3 ML of oxide; 2.3 ML is the saturation coverage of oxygen. The hydroxyl groups are located above any oxide that forms. Independent of the amount of oxide, each surface dehydrogenates when annealed above 220 K due to hydrogen recombination between adjacent hydroxyl groups. By 600 K, only amorphous alumina and a hydride located at the metal-oxide interface remain.
Recommended Citation
Bushby, Stephen James, "Studies Of The Interactions Of Oxygen And Water With Aluminum(100)" (1992). Digitized Theses. 2078.
https://ir.lib.uwo.ca/digitizedtheses/2078