Growth instability in Cu multilayer films due to fast edge/corner diffusion

The instability observed in Cu∕Cu(100) epitaxial growth by Ernst et al. [Phys. Rev. Lett. 72, 112 (1994)] is studied using serial kinetic Monte Carlo (KMC) simulations as well as a recently proposed algorithm for parallel KMC. Our parallel algorithm allows us to simulate longer time scales which are not easily accessible by a serial Monte Carlo simulation. Two different sets of activation barriers were used---one based on effective medium theory and the other based on the embedded-atom method. In both cases, we find that the existence of very fast edge diffusion along close-packed step edges along with a slight enhancement of the rate of corner diffusion is crucial to explaining the experimental results. Some possible mechanisms for this enhancement are discussed.