AVS 49th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP19
Temperature Dependence of Self-Assembled Pb Domains on Cu(111)

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: R. van Gastel, Sandia National Laboratories
Authors: R. van Gastel, Sandia National Laboratories
N.C. Bartelt, Sandia National Laboratories
G.L. Kellogg, Sandia National Laboratories
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Pb deposited on Cu(111) organizes into self-assembled domain patterns.@footnote 1@ It has been hypothesized that stress differences between the Pb/Cu surface alloy-phase and the Pb overlayer phase stabilizes the domains.@footnote 1@ The domain patterns can be ordered arrays of dots (``droplet'' or ``inverted droplet'' phase) or alternating rows (``striped'' phase). Their structure evolves as a function of Pb coverage. The feature size, area fraction and degree of long range order of the domain patterns also show a strong dependence on temperature. To understand this behavior, we have investigated the temperature dependence of the domain boundary energy by studying the thermal fluctuations of striped patterns. We observed an increase in thermal fluctuations with increasing T. Our measurements show that the boundary energy decreases by a factor three in the temperature range 570 K to 640 K. Since theory predicts that the stripe width decreases with decreasing boundary energy, this observation can explain the observed T dependence of the stripe pattern. The absolute value of the boundary energy provides an estimate of the surface stress - we discuss this number in the context of first principles calculations. We have also measured the change in area fraction with temperature of the surface alloy and overlayer phases. We observe a decrease in area fraction of the surface alloy phase with increasing T. We attribute this change in area fraction mainly to a change in the Pb-density of the alloy phase. This work was performed at Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy under Contract DE-AC04-94AL85000. @FootnoteText@ @footnote 1@R. Plass, J. Last, N. C. Bartelt and G. L. Kellogg, Nature 412, 875 (2001).