Thermally induced coarsening was studied in bilayer islands of ordered Al-Pd surface alloy on Pd(001). The island size distribution was deduced from scanning tunnelling microscopic images after annealing the surface at 500 to 700K. The normalized size distribution function, after annealing at 500K (where the bilayer surface alloy formed), exhibited a sharp peak at u ~ 0.2 (where u was the island-size normalized by the average

size) with a long tail extending to u ~ 4. Upon annealing at higher temperatures, the peak shifted to larger u-values and became broader. After annealing at 700K (where decomposition of the surface alloy began), the normalized distribution function closely resembled the universal scaling function which was predicted for coarsening that was due to the diffusion and coalescence of 2-dimensional islands. The data were not consistent with Ostwald ripening.

Diffusion and Coalescence of Bilayer Surface-Alloy Islands of Pd (001)-p(2 x 2)-p4g–Al. T.Aruga, K.Kishi, M.Nishijima: Surface Science, 2001, 493[1-3], 325-30