Nanoparticles of Cu have been made in zinc oxide crystals by ion implantation. The Cu ions were implanted at 400 keV into the (0001) face of a single crystal. After implantation and after post-irradiation annealing there are numerous changes in the luminescence responses which include a variety of green and yellow emission bands. Following annealing at temperatures up to 1000 degrees C a green luminescence near 525 nm was observed which has been associated with the isolated Cu ions. The changes between as implanted and annealed luminescence signals suggests that the implants generate clustering or nanoparticle formation of Cu but anneals dissociate them. (c) 2006 Elsevier B.V. All rights reserved.