Room temperature ferromagnetism is observed in ZnFeO thin films with different Fe content prepared by thermal oxidation of ZnFeS thin films. ZnFeS thin films were grown on c-plane sapphire substrate by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) equipment. The X-ray diffraction (XRD) patterns indicated that a transformation from ZnFeS to ZnFeO has taken place at optimum annealing temperature of 800 degrees C, and the d(0 0 2) values were gradually enlarged with increasing Fe content and it further indicates Fe atoms substituting for Zn atoms in the lattice. The images of field-emission scanning electron microscope (SEM) of ZnFeO thin films show that the grain size increases with increasing Fe content. It was found that the ZnFeO thin films were ferromagnetic above room temperature. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.