Metastable misfit dislocations during thin-film growth: The case of Cu on Ru (0001)

We have used low-energy electron microscopy (LEEM) to study how misfit dislocations evolve in the first atomic layer of Cu deposited on Ru(0001). At equilibrium the Cu islands are pseudomorphic and dislocation-free. However, the islands develop dislocation networks as they grow during deposition. These dislocations are metastable: after deposition ceases, the dislocated area shrinks as adatoms ejected from the network travel to the Cu-island edges. We analyze the dislocation decay rate and find no evidence of a significant energetic barrier for Cu adatoms to exchange with the dislocated phases. Instead, the metastable film's decay is consistent with adatom diffusion being the rate-limiting factor. A small barrier for changing misfit-dislocation density has a consequence - as a film's chemical environment changes during catalysis, its dislocation density can rapidly respond.