Monovacancy and Interstitial Migration in Ion-Implanted Silicon

The migration of monovacancies ($V^0$) and self-interstitials ($I$) has been observed in ion-implanted low-doped float-zone silicon by variable-energy positron annihilation spectroscopy. $V^0$ and $I$ were created by the in situ implantation of $\sim 20\mathrm{keV}$ helium ions below 50 K. Monitoring the time evolution of the vacancy response during isothermal heating enabled the measurement of activation energies for $V^0$ and $I$ migration of 0.078(7) and 0.46(28) eV, respectively. In highly As-doped Si, partial $V$ annihilation occurs via free $I$ migration, with a second stage of annealing, probably associated with $V$-As complexes, above room temperature.