Photoluminescence and Raman studies of the structure of a thick porous silicon film

A porous silicon film fabricated by anodic etching is studied over the thickness (d = 50 +/- 2 A mu m) by Raman scattering (RS) and photoluminescence (PL) methods. It is shown that the porous film structure varies over its thickness. Thus, silicon crystallite sizes increase as approaching the substrate. The PL intensity increases as approaching the film surface, while the position of the PL band maximum varies weakly. It is concluded that the surface effects on the silicon crystallite surface rather than the particle size (quantum-size effect) play a significant role in the PL process.