Characterization of photoluminescence of β-FeSi₂ thin film fabricated on Si and SIMOX substrate by IBSD method

Fe is deposited on a single crystal bulk Si (1 0 0) and separated by implanted oxygen (SIMOX) substrate by the use of ion beam sputter deposition (IBSD) method to form β-FeSi₂ film. Photoluminescence (PL) is measured for these films, after the films on Si substrate are thermally annealed at 1153 K for 24 h. The PL intensity at around 0.83 eV dramatically increased. Such feature has not been seen on SIMOX substrate. To understand how the structural and compositional properties of the film and the substrate affect the PL characteristics, cross-sectional transmission electron microscopy (XTEM) has been applied. The results revealed that these films have quite different structures after thermal annealing due to aggregation of the film. In the bulk Si case, β-FeSi₂ has a particle size of about 200 nm, whereas on SIMOX, it has particle sizes of about 20-30 nm on insulator. Moreover, β-FeSi₂/Si interface remains in the former but not in the latter case. It is revealed that these structural properties are important for enhancement of PL intensity.