Scanning tunneling microscopy observations show that (i) the lattice mismatch between Ni and Ru leads to a sequence of increasingly relaxed structures in Ni films grown on Ru(0001), and (ii) the density of Ni islands changes drastically with the thickness of the underlying Ni film. The latter is associated with an increase in Ni mobility; from monolayer to three-layer Ni films a reduction in Ni adatom diffusion barrier of 300 meV is estimated. Such effects are shown to significantly affect film growth and, in this case, to promote smoother growth. New possibilities for obtaining smoother film growth for heteroepitaxial systems, in general, are discussed.

• Received 7 October 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.3864