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 r ipening, due to their much lower diffusivity. An asymmetric transition region separates these two regimes, characterized by a near-percolati ng structure which undergoes self-similar coarsening.