The crystallographic orientation relationships and the formation process of beta-FeSi2/Si(001) films were investigated by transmission electron microscopy. A film produced by sputtering pure iron onto a silicon substrate at 600 degreesC consists of alpha- and beta-FeSi2 particles. The crystallographic relationships obtained are: (112)(alpha)\\(111)(Si) and (101)(beta)\\(111)(Si) or (110)(beta)\\(111)(Si). Thegrains of alpha- and beta-FeSi2 grown inside the substrate adopt the epitaxy to Si(111), irrespective of the surface orientation of the substrate. At 500 degreesC, on the contrary, there are few aFeSi2 grains and some grains of beta-FeSi2 with (100)(beta)\\(001)(Si) [010](beta)\\[110](Si). These results demonstrate that the lower temperature and the higher Fe concentration suppress the formation of alpha-FeSi2 and promote the formation of beta-FeSi2 on/below the substrate surface. (C) 2004 Elsevier B.V. All rights reserved.