Impurity Decoration for Crystal Shape Control: C$_{60}$ on Ag(111)

ORAL

Abstract

The decoration of hexagonal Ag/Ag(111) monolayer islands by chains of C$_{60}$, observed via STM at 300K, dramatically changes their shape and fluctuations. We tune coverage so that a single C$_{60}$ chain fully decorates each Ag island boundary.\footnote{C.G. Tao et al., PRB 73, 125436 (2006); Nano Letters 7, 1495 (2007).} The C$_{60}$-induced rounding appears due to competing energetic and entropic effects.\footnote{T.J. Stasevich \& TLE, (SIAM) Multiscale Model. Simul. 6, 90 (2007)} We estimate the Ag - C$_{60}$ and C$_{60}$ - C$_{60}$ attractions as $\sim$0.13 eV and $\sim$0.04 eV, respectively.\footnote{T.J. Stasevich et al., submitted.} The edge fluctuations are remarkable: 1) C$_{60}$ decoration does not notably impede the step-edge diffusion (SED) and 2) while the bare-island fluctuations are driven by SED, the decorated island has the signature of non-conserved dynamics, even though the C$_{60}$s remain at the island edge. We suggest that rapidly diffusing Ag atoms randomly attracting the nearby C$_{60}$s. Generalizations of our model show that both spherical and rectangular decorating molecules will similarly lower the energy of highly-kinked boundaries, leading to similar island shape changes.

–

Authors

  • T.J. Stasevich

    U. of Maryland, College Park

  • C.G. Tao

    Department of Physics \& MRSEC, University of Maryland, College Park, U. of Maryland, College Park, University of Maryland, University of Maryland, College Park

  • W.G. Cullen

    Department of Physics \& MRSEC, University of Maryland, College Park, U. of Maryland, College Park, University of Maryland, University of Maryland, College Park

  • Ellen Williams

    Department of Physics \& MRSEC, University of Maryland, College Park, Dept. of Physics, University of Maryland, College Park, MD, Dept. of Physics, University of Mayland, College Park,MD 20742-4111 USA, U. of Maryland, College Park, University of Maryland, University of Maryland, College Park, University of Maryland - College Park, Department of Physics and Materials Research Science and Engineering Center, University of Maryland, College Park, MD 20742

  • T.L. Einstein

    University of Maryland, U. of Maryland, College Park, University of Maryland, College Park