AN ANGLE-RESOLVED SECONDARY ION MASS SPECTROMETRY INVESTIGATION OF ADSORBATE STRUCTURE ON SINGLE CRYSTAL METAL SURFACES

Secondary ion mass spectrometry (SIMS) has not only proven to be a valuable research tool for studies in the areas of heterogeneous catalysis and organic mass spectrometry, but has also seen wide applicability for the analysis of semiconductors. Adsorbate-substrate interactions may be investigated through the measurement of the secondary ion angular and energy distributions. Since these distributions are sensitive to the overlayer structure and adatom site position, the actual arrangement of surface atoms may be determined. Comparison of experimental results to calculated results allows more insight to be gained regarding the complex processes of secondary ion emission and adsorbate-substrate interactions.; It is the intent of this thesis to illustrate the use of the static SIMS and angle-resolved SIMS (ARSIMS) approaches to characterize atomic and molecular adsorbates on two well-ordered single crystal surfaces. These experiments reveal both the sensitivity and wide applicability of ARSIMS as a surface analytical probe. The first single crystal which is studied is the (111) face of the Ni(,3)Fe alloy. Since both metals are catalytically active in Fischer-Tropsch processes, the adsorption of O(,2) and CO on this surface is investigated. In an attempt to further investigate the CO adsorption process, the experimental results are compared to results obtained from molecular dynamics calculations in which the CO molecule is placed in two different bonding sites.; Experiments performed on the second single crystal, Ag(110), are based on the important industrial reaction of ethylene epoxidation. This reaction occurs over various Ag catalysts. Chlorine, which can be present in small amounts on the catalyst, acts as a moderator to increase the selectivity while decreasing the overall activity of the reaction. A Ag(110) surface is used to investigate the adsorption properties of Cl(,2) at room temperature. Alkali metals, which are a constant contaminant on many surfaces, are known to cause modifications to many surface properties. The interaction of Cs with the Ag(110) surface and its effect on oxygen adsorption is also studied. The results indicate that the presence of Cs can modify the structure and alter the reactivity of the surface.