Photochemical synthesis of porous silicon thin films

Porous silicon thin films were produced by photochemical synthesis~with a solution of hydrofluoric acid (HF) and the oxidizer cobalt~nitrate (Co[NO$_{3}$]$_{2})$. An 11mW HeNe laser was used during synthesis to produce the local electric field~necessary for the formation of the porous matrix on the surface of the~crystalline silicon substrate. Substrates used were n-type (Antimony), and p-type (Boron). Samples~prepared with variations in process time from 15 minutes to 5 hours~were examined using photoluminescence, SEM and Raman spectroscopy. Results indicate that the presence of the~oxidizer during synthesis enhances the intensity and persistence of p-Si~photoluminescence when~compared with samples prepared using only HF. In addition, post process~analysis reveals that the porous layer on the samples is present only~on samples processed for less than 4 hours.