Iron silicide island growth on Si(100)2 x 1 surface, silicon growth over iron silicide nanosize islands and structure of silicon and buried iron silicide nanocrystallites have been studied by low electron energy diffraction, atomic force microscopy and high resolution transmission electron microscopy. The best crystal quality of the continuous monocrystal silicon layer and minimal roughness have been observed for the silicon growth temperature T=700 degrees C and silicon layer thickness 100 nm. Nanocrystallites of two types have been observed: small (5-6 nm) and large (30-50 nm). A model of silicon growth atop Si(100) substrate with nanosize iron silicide islands at different substrate temperatures has been proposed. The crystal structure and sizes have been determined for beta-FeSi2 and gamma-FeSi2 nanocrystallites. (C) 2007 Elsevier B.V. All rights reserved.