AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM9
Metastable Pb Microcrystals on Ru(0001) Formed by Oxygen Segregation*

Tuesday, November 5, 2002, 11:00 am, Room C-110

Session: Diffusion & Growth on Metal Surfaces
Presenter: D.B. Dougherty, University of Maryland
Authors: D.B. Dougherty, University of Maryland
K. Thuermer, University of Maryland
J. Reutt-Robey, University of Maryland
E.D. Williams, University of Maryland
Correspondent: Click to Email
Microcrystals formed after dewetting a continuous Pb film grown on Ru(0001) have provided a convenient model system for understanding a variety of surface mass transport issues.@footnote 1,2@ In particular, the relaxation of crystallites toward thermodynamic equilibrium has been studied in detail. Here we report the formation of an unusual metastable crystallite shape and its STM tip induced rapid decay. Combined AES and STM investigations show that this new behavior is the result of minute amounts of oxygen that segregates from the substrate into the Pb. AES is used to observe the segregation of oxygen from the Pb/Ru interface to the surface of the continuous Pb film upon post-deposition annealing. This effect, when combined with the absence of any other detectable contamination explains the presence of nearly spherical crystallites on a surface for which the overwhelming majority have long since decayed to a steady, facetted shape. The decay of the unusual crystallites is induced by repeated scanning of an STM tip, suggesting the removal of a low-mobility oxygen species. This interpretation is consistent with previous observations of the effect of oxygen on single crystal Pb(111) surfaces@footnote 3@ and our Auger analysis. The highly nonequilibrium tip-induced decay is compared with the previously studied decay of Pb microcrystals. * Work supported by UMD-NSF-MRSEC. @FootnoteText@ @footnote 1@ K. Thuermer et al., Step Dynamics in 3D Crystal Shape Relaxation. Phys. Rev. Lett 87 186102 (2001)@footnote 2@ A. Emundts et al., Experimental Absolute Step and Kink Formation Energies on Pb(111) Vicinal Surfaces. Surf. Sci. 496 L35-42 (2002)@footnote 3@ L. Kuipers et al., Jump to Contact and Neck Formation Between Pb Surfaces and a STM tip. Surf. Sci. 340 231-244 (1995).