Photoluminescence, Raman scattering, and infrared absorption studies of porous silicon

Porous silicon layers prepared by anodic dissolutions of silicon wafers in aqueous HF solutions reveal either crystalline phase or intermediate phase between microcrystalline and amorphous phases, depending on the anodization conditions. The configurations of hydrogen and oxygen atoms near the surface of microstructures are directly related to the light emitting characteristics of porous silicon layers. We observed that oxidation leads to the shifts of SiHn stretching modes to higher frequencies and enhanced photoluminescence intensity, which can be correlated with a charge transfer within O—Si—H bonds. We also observed that chemical treatments in trichloroethylene have similar effects as thermal oxidation.