The behavior of Mn when doped into ZnO by ion implantation was investigated by scanning transmission electron microscopy, electron energy loss spectroscopy and dispersive X-ray spectroscopy. Unlike the previously reported case of Co/Ni-implanted ZnO (where Co/Ni nanocrystals were observed.) Mn implantation has been found to induce an O deficiency in ZnO, which results in the formation of hexagonal Zn nanocrystals when the implantation dose is sufficient. Further annealing of the high-dose Mn-implanted ZnO promotes the formation of ZnMn2O4 compounds near the surface and a porous structure within the implanted region. The fundamental reasons behind these physical phenomena are discussed. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rigths reserved.