EFFECT OF STRAIN ON SURFACE-DIFFUSION AND NUCLEATION

The influence of strain on diffusion and nucleation has been studied b y means of scanning tunneling microscopy and effective-medium theory f or Ag self-diffusion on strained and unstrained (111) surfaces. Experi mentally, the diffusion barrier is observed to be substantially lower on a pseudomorphic Ag monolayer on Pt(111), 60 meV, compared to that o n Ag(111), 97 meV. The calculations show that this strong effect is du e to the 4.2% compressive strain of the Ag monolayer on Pt. It is show n that in general isotropic two-dimensional strain as well as its reli ef via dislocations have a drastic effect on surface diffusion and nuc leation in heteroepitaxy and are thus of significance for the film mor phology in the kinetic growth regime.