EFFECT OF KINKS AND CONCERTED DIFFUSION MECHANISMS ON MASS-TRANSPORT AND GROWTH ON STEPPED METAL-SURFACES

We study the effect of kinks and concerted atomic mechanisms on diffus ion processes relevant to metal-on-metal homoepitaxy on fee metal surf aces vicinal to the fee (100) direction. First, we carry out extensive finite-temperature molecular dynamics simulations based on the effect ive medium theory to search for diffusion mechanisms that dominate the mass transport perpendicular and parallel to step edges. Then, the en ergetics 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 kin ks and concerted exchange is found to be able to remove locally the st ep edge barrier for mass transport across the step. The relative impor tance of some of the processes depends on the local tilt of the interf ace, We report results for copper, silver, and nickel, and discuss the generic features of energetics of diffusion processes in effective me dium theory and other semi-empirical many-atom models. We also conside r the implications of our results on surface growth and for models of surface growth under molecular beam epitaxy conditions. (C) 1997 Elsev ier Science B.V.