Lattice sites and damage annealing of implanted Tm and Er in Si

We have studied the lattice sites of Er in CZ Si single crystals by using conversion electron emission channeling from the isotope $^{167m}$Er (2.28 s) which is the decay product of radioactive $^{167}$Tm (9.25 d). Following 60 keV implantation of $^{167}$Tm at a dose of 4 $\times 10^{13}$ cm$^{-2}$ and annealing at 600°C, more than 90% of $^{167m}$Er is found close to tetrahedral insterstitial (T) sites. The tetrahedral fraction of $^{167m}$Er decreases considerably after 10 min annealing at 800°C and above. We attribute this to the onset of diffusion of the parent $^{167}$Tm and its trapping at other defects, presumably oxygen atoms or clusters of Tm/Er.