Ion beam mixing has been extensively used in Metal/Silicon systems to produce the new phases. In the present study a Fe films was deposited by thermal evaporation onto p-type Si(111). The films were irradiated with 300 keV Xe$^+$ ions at room temperature (RT) and subsequently annealed. The experimental results have shown that the Xe irradiation at RT leads to the formation only of the $\varepsilon$-FeSi phase, and after thermal annealing the Fe layer is transformed to a mixture of $\varepsilon$-FeSi, $\alpha$-FeSi$_2$ and $\beta$-FeSi$_2$ phases. The $\beta$-FeSi$_2$ having a direct band gap of 0.81 eV, is demonstrated.