Photoluminescence (PL) spectral change in porous silicon (PS) was investigated during post-anodization in 0.1 kmol/m3 KCl and 0.1 kmol/m3 HClO4 aqueous solutions. The PL intensities of the PS immersed in both solutions were enhanced with an increase of the current density of anodization. The PL enhancement occurred without either change in the size of the silicon nano-crystallites in the PS or chemical properties of the PS. When the PS was made free of anodization, the PL reverted to the initial state. However, the rate at which the PL was restored to the initial state was higher in the KCl solution than in the HClO4 solution. These results suggest an involvement of the anionic species in the PL enhancement.
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