PREPARATION AND CHARACTERIZATION OF SOLID SURFACES WITH ENERGETIC ION BEAMS
Abstract
The interaction of energetic ion beams with solid surfaces forms the basis of both material preparation techniques such as ion implantation and surface characterization methods such as secondary ion mass spectrometry (SIMS). Some fundamental aspects of these techniques have been explored in efforts to gain an understanding of the underlying physical processes. For example, x-ray photoemission spectroscopy has been used to probe the electronic structure of gold, silver, and copper ions implanted in a chemically unreactive silica substrate. The dopant species are observed as isolated, non-interacting atoms whose photoemission and Auger levels may be accurately predicted by an atomistic model which incorporates matrix-related and extra-atomic relaxation corrections to measured gas phase free atom energy levels. Further studies of nickel atoms implanted in a carbon substrate indicate that the model can be useful in predicting the electronic structure of atomic dopants in noninsulating matrices, and is sensitive to configuration changes which occur upon implantation. It is suggested that the described techniques provide a novel approach to preparing model systems of support catalysts. The ejection of substrate particles by impinging ion beams is the primary process in secondary ion mass spectrometry. An energy- and angle-resolved SIMS instrument has been constructed which allows investigation of the mass, energy, and spatial dependence of the secondary ion emission process. The results of experiments performed on clean and c(2 x 2)-CO covered Ni(100) are interpreted in light of molecular dynamics calculations which model the ejection of uncharged particles as momentum is dissipated throughout the crystal after the ion impact event. Correction of the predicted neutral particle trajectories for the image force interaction between the leaving secondary ion and the metal surface results in excellent agreement between theory and experiment. The combination of energy- and angle-resolved SIMS experiments with the insight gained from the dynamics procedure promises to be a fruitful approach to fully characterizing this aspect of ion-surface interaction.
Degree
Ph.D.
Subject Area
Analytical chemistry
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