Corner diffusion is shown to play a crucial role in determining the asymptotic mound coarsening exponent n in the case of unstable epitaxial growth on $\mathrm{}\left(001\right)\mathrm{}$ and $\mathrm{}\left(111\right)\mathrm{}$ surfaces. For the case of island-relaxation without corner diffusion the asymptotic exponent is found to satisfy $n\simeq 1/4.$ However, when rapid corner-diffusion is allowed, the coarsening exponent is found to approach $1/3.$ An explanation for these results is presented in terms of the effects of corner diffusion on the surface current and mound morphology.

• Received 19 August 1999

DOI:https://doi.org/10.1103/PhysRevB.60.R11317