Lattice location of implanted Cu in Si

We have implanted the radioactive probe atom $^{67}$Cu ($t_{1/2}$=61.9 h) into single-crystalline Si. Monitoring the $\beta^{-}$-emission yield from the decay of $^{67}$Cu to $^{67}$Zn as a function of angle from different crystallographic directions allows to determine the lattice location of the Cu atoms by means of the emission channeling effect. We give direct evidence that the majority of implanted Cu occupies near-substitutional sites. As most-likely lattice location we suggest a displacement of 0.51(7) along <111> directions from substitutional sites to bond center positions. The annealing behavior shows that near-substitutional Cu is remarkably stable, and we estimate a dissociation energy of 2.2(3) eV.