AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS3+NS-WeA

Paper SS3+NS-WeA6
Control of Monolayer Island Vacancies on Pt(111) and their Impact on Surface Chemistry

Wednesday, October 27, 1999, 3:40 pm, Room 604

Session: Islands, Clusters, and Steps
Presenter: K. Nafisi, University of California, Irvine
Authors: K. Nafisi, University of California, Irvine
J. Samu, University of California, Irvine
J.C. Hemminger, University of California, Irvine
Correspondent: Click to Email
Michely and Comsa@footnote 1@ have demonstrated that argon ion sputtering Pt(111) at elevated temperature will create ordered monolayer deep island vacancies. We show, by varying the surface temperature parameter, that it is possible to control the size of these vacancies over the range of 30Å to 400Å. We have used a variable temperature, scanning tunneling microscope (STM) to quantify the formation of the island vacancies. We have also used the STM to investigate the dehydrogenation of a series of mono-olefins to form carbon particles at 700 K. The carbon particles were formed both on a clean, annealed, and on sputtered Pt(111) surfaces. The carbon particles are randomly distributed over the surface, and show no preference for formation at particular surface features such as step edges. Also, the formation of the carbon particles is not influenced by large monolayer island vacancies. However, on a surface, where smaller island vacancies have been formed, the carbon particles show a preference of forming on the terraces and not inside of the island vacancies. The difference in behavior between large vacancy islands and small vacancy islands (d @<=@ 40Å) can be explained if molecular diffusion across steps is slow and dehydrogenation products initially decorate the walls (steps) of the vacancy islands. We have also studied the impact of sputtering the sample prior to olefin adsorption with the incident ion beam at an angle away from the surface normal. The carbon particles formed on such surfaces are highly spatially aligned. @super *@This work was supported by the US Department of Energy, Office of Basic Energy Sciences. @FootnoteText@ @footnote 1@ T. Michely and G. Comsa, Nucl. Instr. and Meth., B82, 207 (1993).