Study of precipitate in Si-rich SiO2 films

Silicon precipitates have been obtained in layers of Si-rich SiO2 by ion implantation and thermal treatments. Positron annihilation spectroscopy (PAS) has been used to investigate on open volume defects existing in the oxide; other structural information has been obtained by Raman and Fourier transform infrared (FTIR) spectroscopy. Changes in positronium (Ps) formation and trapping in the implanted layer were observed. The Ps signal decreases after Ar+ ion bombardment, which induces a substantial breaking of both SiH and SiO bonds. Comparison with Raman measurements suggests that this effect is indirectly related to the formation of Si nano-precipitates. A strong increase of the Ps signal in the implanted samples is observed after thermal treatments at 500 and 800 °C, followed by a new decrease after a thermal treatment at 1100 °C.