The Roles of Lattice Vibrational Excitation and Product Electronic Excitation in Dissociative Chemisorption on Covalent Solids

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This research project, supported by the Analytical and Surface Chemistry Program, is concerned with the dynamics of halogen interactions with silicon surfaces. Using molecular beam scattering methods, Professor Ceyer and her colleagues at MIT will test the hypothesis that the high reactivity of XeF2 (as compared with F atoms) with silicon is due to the large energy transfer that occurs upon collision of the XeF2 molecule with the silicon lattice. This is counter to what would be expected thermodynamically. Using a range of fluorine`carriers` with differing masses, this hypothesis will be directly tested. In addition, the detailed dynamics of abstractive chemisorption will be probed by monitoring emission from electronically excited XeF* species which may result from the interactions of XeF2 with the silicon surface. The etching of silicon by fluorine containing species forms a part of silicon etching technology, with applications in the production of electronic devices. This research project addresses fundamental questions about the dynamics of surfaces. Using a range of molecular beam and surface sensitive spectroscopic methods, the effect of collisional excitation of the silicon lattice on the reaction dynamics will be probed. The dynamics of abstractive dissociative chemisorption of fluorine containing molecules will also be investigated.