Film stress and microstructure evolution during the growth of a Ni bicrystal film are investigated by molecular dynamics simulations. The nominal surface orientation of the growing film was (111) and the grain boundaries are $\Sigma 79$ symmetrical tilt grain boundaries. The growth mode is layer by layer; two-dimensional (2D) islands nucleate on the surface, grow, and coalesce into complete layers. Grain-boundary migration near the free surface is observed as boundaries are dragged by step edges of growing 2D islands. Simulations show that the film stress-thickness product is compressive and oscillatory with a period that is approximately equal to one monolayer. Adatoms are observed to incorporate into grain boundaries and exert compressive strain on neighboring grains. Theoretical modeling demonstrates incorporated atoms are a primary source of the observed compressive stress during growth and gives predictions in very good agreement with simulation results. The oscillatory stress-thickness product is shown to be related to atoms diffusing into the grain boundary from the surface and out of the grain boundary onto the surface.

• Received 23 May 2008

DOI:https://doi.org/10.1103/PhysRevB.79.224113