Coarsening mechanisms in a metal film: From cluster diffusion to vacancy ripening

Coarsening of Ag films on Ag(100) at room temperature occurs primarily via diffusion-mediated coalescence of two-dimensional adatom clusters, rather than by Ostwald ripening, up to a coverage of 0.65 monolayer. Above 0.8 monolayer, vacancy clusters coarsen primarily via Ostwald ripening, due to their much lower diffusivity. An asymmetric transition region separates these two regimes, characterized by a near-percolating structure which undergoes self-similar coarsening.