Effect of kinks and concerted diffusion mechanisms on mass transport and growth on stepped metal surfaces

Abstract

We study the effect of kinks and concerted atomic mechanisms on diffusion processes relevant to metal-on-metal homoepitaxy on fcc metal surfaces vicinal to the fcc (100) direction. First, we carry out extensive finite-temperature molecular dynamics simulations based on the effective medium theory to search for diffusion mechanisms that dominate the mass transport perpendicular and parallel to step edges. Then, the energetics of these processes are studied by ground state calculations. Our results show that kinks play an important role for diffusion both across and along step edges. In particular, the combined effect of kinks and concerted exchange is found to be able to remove locally the step edge barrier for mass transport across the step. The relative importance of some of the processes depends on the local tilt of the interface. We report results for copper, silver, and nickel, and discuss the generic features of energetics of diffusion processes in effective medium theory and other semi-empirical many-atom models. We also consider the implications of our results on surface growth and for models of surface growth under molecular beam epitaxy conditions.