Abstract
Vapor deposition methods have been used to form continuous films on substrates, however, formation of nanoislands at the initial deposition stage is recently gathering interests from the viewpoint of nanotechnology. Especially for non-epitaxial growth, various nanostructural changes appear. But non-epitaxy is not understood well compared with epitaxy due to its complicated phenomena. To see the whole picture of non-epitaxial growth, we have introduced a simple concept; thermodynamics controls the unit-structure within the surface diffusion length of deposits whereas kinetics controls the ensemble-structure of larger scale. Based on this concept, various phenomena occurring at the initial stage of non-epitaxial growth are systematized by referring to the results of our continuing research as examples. As is well known, the balance among the surface and interfacial energies of deposits and substrates thermodynamically determines the shape of islands. The balance among bulk, surface, and interfacial energies thermodynamically determines the crystallographic structure of islands, and sometimes amorphous-to-crystalline transition occurs for deposits on amorphous substrates. Both adatom surface diffusion and island migration kinetically affect the structure of island ensembles, and interspacing among islands roughly corresponds to the characteristic length of diffusion and migration. Incubation for deposition appears more frequently in chemical vapor deposition than in physical vapor deposition, which is caused by the changes either in the sticking probability of precursors or in the desorption rate of adsorbates. These insights will help us to understand and control nanostructural evolution during non-epitaxial growth.
