Multiscale modeling of island nucleation and growth duringCu(100)homoepitaxy

Abstract

The long-time scale dynamics of small $\mathrm{Cu}∕\mathrm{Cu}(100)$ islands are studied. Atomistic simulations using embedded atom method (EAM) potentials and the dimer method saddle point searches provide pathways and their temperature-dependent rates to lattice-based kinetic Monte Carlo (KMC) simulations. The KMC utilizes translational symmetry to identify previously visited sites and re-use the atomistic rates. As a result very long time scales are accessible to the simulation which reveals the dissociation as well as the diffusion mechanisms of the small islands in an unbiased manner. Our results for island diffusion reproduce well the activation energies calculated in previous work, and provide in addition the associated frequency prefactors. The island dissociation pathways are rationalized in terms of previously anticipated mechanisms. We also utilize our results in mean field rate equations to predict ``kinetic phase diagrams'' for the critical island size as a function of temperature and vapor deposition rate during $\mathrm{Cu}(100)$ homoepitaxy. We predict that the higher critical island sizes $(i>2)$ should be observable at higher temperatures (above $\ensuremath{\sim}500\phantom{\rule{0.3em}{0ex}}\mathrm{K}$) at experimentally accessible deposition rates.