RUI: Structural Evolution of Bimetallic Deposition Systems

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9974545RoelofsThis Research at Undergraduate Institutions (RUI) award supports theoretical research to explore the evolution of heteroepitaxial, deposition systems. Homoepitaxial growth systems are now reasonably well understood for many systems so that coming to terms with the challenges of bi-metallic systems is the next natural step toward a full understanding of epitaxial growth phenomena. There is a strong technological motivation for such progress in that bi-metallic systems encompass surface alloy systems and also have important relevance for surface magnetism and catalysis. Recently the PI has modeled a prototypical bi-metallic, epitaxial system, the deposition of submonolayer amounts of Rh on the Ag(001) surface. Extensive scanning tunneling microscopy (STM) results are available for this system and these display several unusual structural features, most notably the occurrence of holes in the silver substrate. The PI has developed a model for treating the surface kinetics of this and similar systems at the atomic level, a detailed account, in other words, for the atomic scale movements that occur to produce the structures seen. The model is based on a simple, but physically reasonable approximation for the energy barriers governing local atomic arrangement, which forms the basis of a powerful simulation program which generates and characterizes the evolution of the resulting surface features. This approach has already succeeded in qualitatively accounting for the interesting structures seen for the Rh/Ag(001) system, and a first report has recently been submitted for publication. The present work will extend this treatment and model other regimes and systems in collaboration with the experimental group of Behm in Ulm, Germany. Behm's group has extensive experimental capability for study of bi-metallic growth systems an is in fact the source of much of the STM data for the Rh/Ag(001) system. Further refinement of our model for the Rh/Ag(001) system is needed and it will be extended to the multi-layer case and to other temperature regimes. The modeling will be applied to other bi-metallic growth systems, including some with catalytic relevance. We are also capable of producing important fundamental results on the role of vacancies and adatoms in the formation and rearrangement of complex surface structures.This Research at Undergraduate Institutions (RUI) award supports theoretical research to explore the evolution of heteroepitaxial, deposition systems. Homoepitaxial growth systems are now reasonably well understood for many systems so that coming to terms with the challenges of bi-metallic systems is the next natural step toward a full understanding of epitaxial growth phenomena. There is a strong technological motivation for such progress in that bi-metallic systems encompass surface alloy systems and also have important relevance for surface magnetism and catalysis. The theoretical work will be done in collaboration with an experimental group in Germany.