AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA1
Mechanisms and Energetics in Diffusion of O2-Molecules and H-atoms on Si(1x1)-7x7 Surfaces

Tuesday, October 26, 1999, 2:00 pm, Room 607

Session: Diffusion on Surfaces
Presenter: R.L. Lo, Academia Sinica, Republic of China
Authors: R.L. Lo, Academia Sinica, Republic of China
I.S. Hwang, Academia Sinica, Republic of China
M.S. Ho, Academia Sinica, Republic of China
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Using a variable temperature STM, atom and molecular dynamics on solid surfaces can be observed directly and the energetics studied in detail. It is possible to trace the path of single particle movement, measure site and path specific hopping rates and the rate parameters of individual atoms and molecules on solid surfaces as well as to probe the mechanisms. We find that on Si(111)-7x7 surface, O2 molecules adsorb on top of adatom sites while H atoms adsorb on top of rest atom sites. Diffusion and hopping of H and O2 on this surface is achieved by hopping of chemical bonds via intermediate states. We have identified the intermediate states and also derived site and path specific activation energies and frequency factors, and the potential energy curves for the hopping of O2 and H on this surface. The physical significance of these measurements will be discussed. Research supported by NSC of ROC and Academia Sinica. 1. I-S Hwang, R-L Lo and T. T. Tsong, Phys. Rev. Lett. 78, 4797 (1997). 2. R-L Lo, I-S Hwang, M-S Ho and T. T. Tsong, Phys. Rev. Lett. 80, 5584 (1998).