Radiation resistance of Fe-Si compounds and its application

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Ion beam sputter deposition (IBSD) method was employed to modify the surface of Si surface by forming a semiconducting β-FeSi_2 layer. It was revealed that, by carefully choosing the sputter etching and thermal annealing conditions, a highly-oriented thin β-FeSi_2 film of 100 nm in thickness, with the epitaxial relationship of β-FeSi_2 100) // Si (100) can be fabricated at 973 K. Further investigation demonstrated that a highly-oriented film can be also formed at much lower temperature, i.e. at 873 K, or can be made thicker by optimizing the substrate temperature, deposited thickness of sputtered atoms and the target compositions.Cross-sectional transmission electron microscope (TEM) images showed that the interface of β-FeSi_2 / Si is atomically flat and continuous, which suggests that this silicide can be used to form heterojunction with Si substrate for device applications. In addition, the surface of silicide was found to be highly resistant to oxidation. Preliminary investigation on the irradiation effects on the silicide film using high-energy (> 100 MeV) heavy ion (Xe ion) revealed that the film became amorphous as the ion fluence was increased, and that no phase transformations could be observed. Photoluminescence measurement proved to be useful to further elucidate irradiation effects on the film and substrate, not to say the optical properties of semiconducting silicide layer.