Study of the trapping of CoFe impurities at the internal wall of nanosized Si voids

The trapping of transition metal impurities to cavities in c-Si recently attracted much interest, stemming from the possibility to use the process for proximity gettering. Mössbauer spectroscopy is employed on ion-implanted {⁵⁷Co}/{⁵⁷Fe} to elucidate the nature of the site of the impurity atom at the internal surface of the voids. We observe a trapping effect upon thermal treatment, hampering normal silicide formation. Also a pre-existing silicide phase can be partially dissolved in favour of cavity trapping. The binding energy for cavity trapping is found to be lower than for silicide formation.