Low-energy electron diffraction (LEED) is used to investigate the initial stages of growth of silicon on Si(111) between 556 and 900 K. The partial coverages θh of the growing film are derived from the intensity variation during evaporation of the 00 and 7 × 7 spot. A preferred growth is observed in the second layer long before the first layer is completed. Surface defects caused by superstructure disorder on the grown islands act as nucleation centers for the diffusing adatoms, so at 633 K substrate temperature the grown islands show no ordered superstructure, although the film is epitaxial. The 7 × 7 spots show all the features of diffraction of a substrate with a non-scattering overlayer for coverages below two monolayers. The grown films show below 650 K an unordered superstructure, in an intermediate temperature range a mixture of 5 × 5 and 7 × 7 domains, and finally, above 870 K, perfect 7 × 7 superstructure. The average size of islands increases from 30 to 40 000 atoms.