Different photoluminescence (PL) spectra were observed for rf sputtered ZnO films when excited with light of different wavelength. When the wavelength of the excitation light was 270 nm, a UV emission peak (356 nm) and a blue peak (446 nm) were generated for the films on sapphire, silicon and quartz substrates. For the films on glass substrates only the 446 nm blue emission appeared. With increasing the wavelength of the excitation light up to 300 and 320 nm, the UV emission disappeared for films on various substrates and the wavelength of the PL peaks increased up to 480 and 510 nm, respectively. When the wavelength of the excitation light increased to 340-395 nm, the PL spectrum became a wide band which was consistent with three emission peaks. (C) 2002 Elsevier Science B.V. All rights reserved.