Photoluminescence from C₆₀-coupled porous structures formed on Fe⁺-implanted silicon

〈111〉-oriented p-type Si wafer with a resistivity of 1-5 Ω cm was implanted with Fe⁺ and then annealed at 1100°C in N ₂ for 60 min, followed by anodization in a solution of HF to form porous structure with β-FeSi₂ nanocrystallites. Photoluminescence (PL) spectral measurements show that a strong PL peak appears in the range of 610-670 nm. The position of the PL peak remains unchanged, but its intensity increases with the storage time in air until about three months and then saturates. C₆₀ molecules were chemically coupled on the porous structure through a kind of silane coupling agent to form a nanocomposite. It is revealed that the stable PL peak monotonically shifts to a pinning wavelength at 570 nm. Experimental results from PL, PL excitation, Raman scattering, and x-ray diffraction measurements clearly show that the pinned PL originates from optical transition in C₆₀-related defect states, whereas the photoexcited carriers occur in the β-FeSi₂ nanocrystallites formed during anodization. This work opens a new way to tailor nanometer environment for seeking optimal luminescent properties. © 2006 American Institute of Physics.