Photoluminescence From Oxidized Macroporous Silicon: Nanoripples and Strained Silicon Nanostructures

We report synthesis of luminescent porous silicon (Si) having uniform macromorphology by sequential oxidation and etching of macroporous Si formed in a hydrofluoric acid and dimethylformamide solution. The macroporous template exhibits room-temperature photoluminescence (PL) with peaks in the blue/green region. Structural investigations reveal the formation of nanoripples and other strained nanostructured Si inside the pores of the oxidized samples. The room-temperature PL disappears, and the structure of the macropores changes on treating the oxidized templates with an alkaline solution. Based on these findings, we explicitly show that the origin of luminescence is due to the presence of nanoripples and strained Si nanostructures. Luminescent macroporous Si therefore reveals interesting physics but are untenable for application of light sources in optoelectronic devices.