Stochastic ripening of one-dimensional nanostructures

Ostwald ripening, in which large clusters grow at the expense of smaller ones, is driven by differences in the chemical potentials of these clusters. We demonstrate that ripening can also occur without chemical potential differences between small and large particles, by observing the exchange of single atoms between linear chains of Ir atoms; on a W(110) surface these dissociate at a rate independent of length. Ripening takes place because of the stochastic nature of individual atomic events, and is characterized by large fluctuations in the number of exchanges for a chain to disappear. This mechanism should be generally applicable in the ripening of one-dimensional chains, formed on metals as well as semiconductors, and for which the dissociation energy is insensitive to length.