High-quality ZnO thin films have been grown on a Si(100) substrate by plasma-enhanced chemical vapor deposition (PECVD) using a zinc organic source (Zn(C2H5)(2)) and carbon dioxide (CO2) gas mixtures at a temperature of 180degreesC. A strong free exciton emission with a weak defect-band emission in the visible region is observed. The characteristics of photoluminescence (PL) of ZnO, as well as the exciton absorption peak in the absorption spectra, are closely related to the gas flow rate ratio of Zn(C2H5)(2) to CO2. Full-widths at half-maximum of the free exciton emission as narrow as 93.4 meV have been achieved. Based on the temperature dependence of the PL spectra from 83 to 383 K, the exciton binding energy and the transition energy of free excitons at 0 K were estimated to be 59.4 meV and 3.36 eV, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.