Photoluminescence and Raman spectral study of porous Si during F₂ exposure

Visible luminescence and Raman spectral changes of porous Si (PS) during F₂ exposure were recorded. F₂ exposure of the PS under Ar⁺ laser light (488 nm) irradiation at 373 K leads to a significant spectral change of photoluminescence (PL). During an early stage of the exposure, the PL band of the 750 nm peak decreased in intensity and a new band emerged at 600 nm. After 30 min, the new band dominated the spectrum while the band at 750 nm almost disappeared. On the contrary, the phonon band due to nanosize Si crystals of the PS remained unchanged. These results suggest that the PL spectral change arises due to a change in the chemical structure of the sample surface.