Surface photoluminescence and magnetism in hydrothermally grown undoped ZnO nanorod arrays

ZnO nanorod arrays were synthesized by a hydrothermal method on the Si substrate with ZnO thin film as seed layer prepared by magnetron sputtering. The presence of -OH ligands on the surface of the as-grown sample was confirmed, and its dominant role in both suppressing the visible emission and boosting the room-temperature ferromagnetism (FM) was revealed. Through alternative H-2 and O-2 annealing to remove the -OH ligands, reconstruct surface-states and tune the oxygen occupancy in ZnO nanorods, the clear correlation between the characteristic green emission and ferromagnetism was established. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705412]