We examine the ramified islands observed in submonolayer $\mathrm{Cu}/\mathrm{Ni}(100)$ growth. Our results indicate that the strain-energy contribution to the dependence of island energy on shape is surprisingly weak. In contrast, our accelerated dynamics simulations indicate that unexpected concerted popout processes occurring at step edges may be responsible. Kinetic Monte Carlo (KMC) simulations which include these processes produce island shapes which are very similar to those observed in experiment. These results suggest that the shape transition is of kinetic origin but is strongly mediated by strain.

• Received 28 October 2011

DOI:https://doi.org/10.1103/PhysRevLett.108.076102