Evidence for vacancies in amorphous silicon

The microscopic nature of defects in ion-implanted amorphous Si has been probed using M\"ossbauer spectroscopy. Analysis of the ¹¹⁹Sn M\"ossbauer spectra obtained from ¹¹⁹Sb in amorphous Si requires two independent sites for Sb in amorphous Si. Direct comparison of the isomer shifts and Debye temperatures of these lines with data from crystal Si demonstrates that the sites are a substitutional network site and an Sb-vacancy complex. The data suggest that point defects analogous to the crystal vacancy exist in the amorphous Si structure.