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.