AVS 50th International Symposium
    Surface Science Monday Sessions
       Session SS3-MoM

Paper SS3-MoM5
Edge Diffusion on Spiral Steps on Pb(111) Microfacets*

Monday, November 3, 2003, 9:40 am, Room 328

Session: Surface Diffusion and Wetting
Presenter: D.B. Dougherty, University of Maryland at College Park
Authors: D.B. Dougherty, University of Maryland at College Park
W.G. Cullen, University of Maryland at College Park
J.E. Reutt-Robey, University of Maryland at College Park
E.D. Williams, University of Maryland at College Park
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A classic source of steps on solid surfaces is a screw dislocation intersecting the surface.@footnote 1@ From the intersection a spiral step emerges that can provide active sites for mass transport. To investigate the local kinetics associated with spiral steps, we have employed highly pure micron-size Pb crystallites grown on Ru(0001) with spiral steps on flat Pb(111) facets. Spiral step fluctuations have been observed with STM from 300-390 K and analyzed using the temporal correlation function and the persistence probability.@footnote 2@ The scaling of both functions points to a rate-limiting relaxation mechanism of step edge diffusion, exactly as observed for steps on single-crystal Pb(111).@footnote 3@ The kinetic parameter governing edge diffusion, the hopping mobility, has been extracted from the temporal correlation function and an activation energy has been extracted from the temperature dependence of the mobility. To investigate step fluctuations away from equilibrium, we have made fluctuation measurements on slowly rotating spiral steps on Pb crystallites in the process of thermal equilibration. The continuous unwinding due to the presence of the dislocation is distinct from the previously observed layer peeling process.@footnote 4@ The magnitude of the temporal correlation function for the fluctuations of a rotating spiral was observed to increase with the spiral curvature. The dynamic scaling was unaffected, showing that edge diffusion is still the rate-limiting transport mechanism. * Supported by UMD-NSF-MRSEC DMR-00-80008. @FootnoteText@ @footnote 1@ W.K. Burton, N. Cabrera, F.C. Frank, Proc. R. Soc. London, Ser. A 243 (1951) 299.@footnote 2@ D.B. Dougherty, O. Bondarchuk, M. Degawa, E.D. Williams, Surf. Sci. 527 (2003) L213. @footnote 3@ S. Speller, et al., Surf. Sci. 331-333 (1995) 1056; L. Kuipers et al., Phys. Rev. B 52 (1995) 11387.@footnote 4@ K. Thurmer, et al., Phys. Rev. Lett. 87 (2001) 186102.