The Fe/Si multilayers were prepared by electron beam evaporation in a cryo-pumped vacuum deposition system. Ag + and Au + ions of 100 MeV at two different fluencies such as 1 × 10 12 ions/cm 2 and 1 × 10 13 ions/cm 2 at a pressure of 10 − 7 torr were used to irradiate the Fe/Si samples. The irradiated samples were analyzed by High-Resolution XRD and it reveals that the irradiated films are having polycrystalline nature and it confirms the formation of the β-FeSi 2. The structural parameters such as crystallite size ( D), strain ( ε) and dislocation density ( δ) have been evaluated from the XRD spectrum. The role of the substrates and the influence of swift heavy ions on the formation of β-FeSi 2 have been discussed in this paper.