Nucleation theory: Present status and outstanding problems

Our understanding of the nucleation and initial stages of growth of amorphous and epitaxial films has developed substantially over the last decade. The outstanding problems are concerned mainly with the distribution of monomer and nucleation rate, the cluster size and spatial distributions and their effects on growth and mobility coalescence. However, since the material parameters which control nucleation behaviour are usually not known, optimum deposition conditions for any application must be found by experiment. Consequently further theoretical refinement over the next decade is unlikely.