The nucleation of silicon nitride on silica by chemical vapor deposition using medium energy ion scattering followed by coalescence was examined. The growth mode merges only after 20-30A has been deposited and the interface formation is responsible for the growth mode. Both nitrides and oxide have low surface energies and the difference in surface free energies greatly affect the morphology. This is due to the arrangement of bond topology on the oxide surface which minimize the growth mode. As a result, there is an increase in energy barrier to wetting but little energy gained for de-wetting.