Rare-earth (RE) Tb3+ ion doped ZnO and Mg0.15Zn0.85O thin films were successfully fabricated by the sol-gel deposition method. The Tb3+ ion was substituted for the Zn2+ ion in the host material, as revealed by X-ray diffraction and optical absorption spectra. The cathodoluminescence properties of the doped samples were also studied. The RE3+ luminescence mechanism is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.