GaN exists in both wurtzite and zinc-blende phases and the growths of the two on its ͑0001͒ or ͑111͒ surfaces are achieved by choosing proper deposition conditions of molecular-beam epitaxy ͑MBE͒. At low substrate temperatures but high gallium fluxes, metastable zinc-blende GaN films are obtained, whereas at high temperatures and/or using high nitrogen fluxes, equilibrium wurtzite phase GaN epilayers resulted. This dependence of crystal structure on substrate temperature and source flux is not affected by deposition rate. Rather, the initial stage nucleation kinetics plays a primary role in determining the crystallographic structures of epitaxial GaN by MBE.

Endohedral metallofullerene Tb@C82 molecules adsorbed on the C60 film and Si(100) 2 × 1 have been investigated by scanning tunneling microscopy (STM). The C60 film was obtained by depositing 2−3 monolayers (ML) of C60 molecules on a highly oriented pyrolytic graphite (HOPG) surface. Tb@C82 molecules have great mobility and aggregate along the edges of terraces on the C60 film, and form a close-packing monolayer with increasing coverage. Very few trimers or dimers were imaged on the surface of C60 film. In contrast, the Tb@C82 molecules were randomly distributed on the surface of Si(100). These nucleation behaviors of Tb@C82 molecules can be explained by the interaction of Tb@C82−Si and Tb@C82−Tb@C82 that were brought on by the permanent dipole moment of Tb@C82 molecules.