The epitaxial growth process of beta-FeSi2 on Si(100) surface under ultrahigh vacuum condition has been studied by low energy electron diffraction (LEED) and low energy ion scattering spectroscopy (LEIS). The LEED pattern of Si (100)-2 x 1 changes into amorphous structure with Fe deposition of about 10 A at room temperature. With annealing at 540 degreesC, the LEED pattern shows 2x2 structure corresponding to the formation of the epitaxial beta-FeSi2 (100) template layer. The alpha-scan in Li+-LEIS and X-ray diffraction (XRD) study strongly suggest that the topmost surface of the 2x2 structure is terminated by Si atoms. By XRD, it is shown that the beta-FeSi2 develops with characteristic orientation even if iron reactant is deposited onto the template surface. (C) 2004 Elsevier B.V. All rights reserved.