Lattice location and stability of implanted Cu in ZnO

The lattice location of copper in single-crystalline zinc oxide was studied by means of the emission channeling technique. Following 60-keV room-temperature implantation at a fluence of 2.3 $\times 10^{13}$cm$^{−2}$, the angular distribution of $\beta^{-}$-particles emitted by the radioactive isotope $^{67}$Cu was measured by a position-sensitive detector. The $\beta^{-}$-emission patterns give direct evidence that in the as-implanted state a large fraction of Cu atoms (60%–70%) occupy almost ideal substitutional Zn sites with root-mean-square (rms) displacements of 0.16–0.17 Å. However, following annealing at 600°C and above Cu was found to be located on sites that are characterized by large rms displacements (0.3–0.5 Å) from Zn sites