Radiation defects in ion-implanted silicon. I. Mössbauer spectroscopy ofSn119defect structures from implantations of radioactive antimony

Impurity-defect structures in silicon containing ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ have been studied by Mössbauer spectroscopy. The defects have been created by isotope-separator implantation of radioactive ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sb}_{}^{+}{}_{}{}^{}$ ions at room temperature. Emission spectra of the 24-keV Mössbauer $\gamma$ radiation from the daughter ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ have been measured. The Mössbauer spectra are analyzed in terms of four independent lines. These lines are characterized by the measured isomer shifts, linewidths, quadrupole splittings, and Debye-Waller factors. From these parameters, different bonding configurations are deduced for the Sn impurity atoms. Thus, the lines are assigned to emitting Sn atoms as substitutional impurities and as atoms in more complex impurity-defect structures. The formation of the impurity-defect structures in the implantation process (and their annealing behavior) is controlled by properties of the antimony atoms, whereas the measured Mössbauer parameters reflect the response of the Sn daughter atoms in these structures. It is concluded that a large fraction of the Sn atoms occupy locally undisturbed, substitutional lattice sites [with an isomer shift of $\delta =1.83\mathrm{}\left(6\right)\mathrm{}$ mm/s and a Debye temperature of $\Theta =220\mathrm{}\left(20\right)\mathrm{}$ K]. A minor fraction is in interstitial lattice positions [$\delta =3.3\mathrm{}\left(1\right)\mathrm{}$ mm/s, $\Theta =240\mathrm{}\left(30\right)\mathrm{}$ K]. Two other lines [$\delta =2.6\mathrm{}\left(1\right)\mathrm{}$ mm/s, $\Delta E_Q\approx 0.3$ mm/s, $\Theta =160\mathrm{}\left(20\right)\mathrm{}$ K, and $\delta \approx 2.6$ mm/s, $\Theta =250\mathrm{}\left(40\right)\mathrm{}$ K] are attributed to vacancy associated Sn impurity atoms. Rough annealing experiments show annealing of the Sb impurity vacancy complex (with $\Theta =160\mathrm{}$ K) between 700 and 900 K. The other impurity-vacancy structure ($\Theta =250\mathrm{}$ K) is only formed after high-temperature treatment of the sample (≳1200 K). The interstitial fraction increases with annealing temperature.