Additive-enhanced coarsening and smoothening of metal films: Complex mass-flow dynamics underlying nanostructure evolution

Exposure of Ag/Ag(100) thin films to molecular oxygen (O-2) at 220-250 K is shown to activate low-temperature coarsening of submonolayer island distributions, and a smoothing of multilayer films with mounded morphologies. Dissociation of O-2 at kink sites populates step edges with atomic oxygen (O), modifying the step-edge energetics, and facilitating Ostwald ripening of film nanostructures. We propose that ripening occurs by easy detachment and terrace diffusion of an AgnO species. Cluster diffusion does not play a significant role, contrasting with the O-free system.