structural properties of mechanically ball-milled porous silicon

A simple powder technique with hydrofluoric (HF) acid leaching technique was presented for the fabrication of bulk porous silicon (PS). Silicon wafers were crushed, ball milled for various milling times and pressed into pellets under the pressure of 4,000 psi (276 bar). Samples were annealed in H2/Ar and in air. Structural properties of PS were investigated using X-ray diffraction technique, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Crystalline size of Si nanoparticles decreased with increase of milling time and can be improved after mechanical pressing and annealing. Obtained PS pellets had uniform porosity. Porosity of the specimen could be significantly increased with the combination of annealing in air to promote the oxide layer on the silicon nanoparticles and HF leaching to form voids by removing the created oxide layer. Preliminary results showed that the percent porosity can be increased up to 43.6%.