Defects in Si-Rich SiO₂ Films Prepared by Radio-Frequency Magnetron Co-sputtering Using Variable Energy Positron Annihilation Spectroscopy

Si-rich SiO₂ films prepared by rf magnetron co-sputtering method are studied by slow positron beams. The negatively charge point defects (probably P_b centres or peroxy radicals) at the silicon nanocluster (nc-Si)/SiO₂ interface are observed by Doppler broadening spectra. Coincidence Doppler-broadening spectra show that positrons have a higher annihilation probability with core electrons nearby oxygen atoms than silicon atoms. The formation of N-related bonds may be the reason for the prevention of the migration reaction of Si and O atoms, hence nc-Si formation is inhibited by annealing in nitrogen compared to in vacuum.