AVS 50th International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM1
Dislocation Mediated Interactions in Self-assembly: The S-induced Triangular Hole-array in Ag/Ru(0001)

Wednesday, November 5, 2003, 8:20 am, Room 327

Session: Surface and Interface Structure: Metals
Presenter: K. Thurmer, Sandia National Laboratories
Authors: K. Thurmer, Sandia National Laboratories
N.C. Bartelt, Sandia National Laboratories
R.Q. Hwang, Sandia National Laboratories
Correspondent: Click to Email
By depositing S onto a monolayer of Ag/Ru(0001) we are able to create very regular arrays of 2D-vacancy islands.@footnote 1@ Real-time STM measurements reveal the mechanisms of such adsorbate induced restructuring: Starting from a herringbone pattern of the clean Ag-film, the S transforms the film by a sequence of dislocation reactions that individually decrease the Ag density. Eventually all threading dislocations are eliminated and the film assumes a Moire-like structure, in which on-top Ag-atoms are replaced by holes filled with S. These holes form a strikingly regular triangular lattice with a nearest neighbor spacing of 5nm. The conventional assumption is that such pattern formation is caused by substrate-mediated long-range elastic interaction. To test this assumption, we have used STM to measure the thermal vibrations of the hole array as a function of temperature. Surprisingly, we find we can account for these observations without invoking substrate relaxations: By comparing the measured vibration amplitudes to 2D Frenkel-Kontorova simulations we find that the hole-array is stabilized by a pattern of partial dislocations connecting the holes. First principles electronic structure calculations of the 2D FK model parameters for Ag/Ru quantitatively reproduce the hole-hole interaction strength extracted from our measurements. @FootnoteText@ @footnote 1@K. Pohl et al. Nature 397 (1999) 238.