Novel Coarsening Behavior of Pb nanocrystals on Si(111)

We show that Pb nanocrystals grown on Si(111)7x7 exhibit novel coarsening behavior that cannot be described by the classical Gibbs-Thomson effect. This system is known for quantum size effects (QSE) that lead to preferred island heights which depend on the coverage and temperature. Using complementary surface x-ray diffuse scattering and STM, we find an unexpected and unusual flux rate dependence, a lack of scaling of the island densities, and island decay times that are orders of magnitude faster than expected from the classical analysis. For example, a highly mono-disperse island height distribution is observed if the islands are grown at high rather than low flux rates. These results have important implications for understanding the controlled growth and self-organization of nanostructures.