In this paper, highly oriented nanocrystals of Fe3Si with a D0(3) structure are fabricated on SiO2 using ultrathin Si on insulator substrate. First, (001) oriented Si nanocrystals are formed on the SiO2 layer by solid state dewetting of the top Si layer. Then, Fe addition to the Si nanocrystals is performed by reactive deposition epitaxy and post-deposition annealing at 500 degrees C. The structures of the Fe-Si nanocrystals are analyzed by cross-sectional transmission electron microscopy and nanobeam electron diffraction. We observe that Fe3Si nanocrystals with D0(3), B2, and A2 structures coexist on the 1-h post-annealed samples. Prolonged annealing at 500 degrees C is effective in obtaining Fe3Si nanocrystals with a D0(3) single phase, thereby promoting structural ordering in the nanocrystals. We discuss the formation process of the highly oriented D0(3)-Fe3Si nanocrystals on the basis of the atomistic structural information. (C) 2013 Elsevier B.V. All rights reserved.