Heat-treatment induced modifications of porous silicon

Positron lifetime spectroscopy was used to investigate a porous silicon film subjected to heat treatments in argon atmosphere. After annealings between 300 and 500 degrees C the mass of the film increased by 17% due to oxygen uptake. Vacancy clusters in the silicon oxide layer covering the nano-crystallites increased their concentration by a factor of 3. Above 900 degrees C significant structural changes of the film took place as manifested by growth in the size of vacancy clusters.