A preferred oriented (0 0 2) ZnO thin films have been grown on Si (10 0) substrate via plasma enhanced chemical vapor deposition using diethylzinc and carbon dioxide as reactant sources. In this paper, the dependence of the quality of the ZnO thin film on the growth temperature is studied. A polycrystalline ZnO thin film with a c-axis-orientated wurtize structure is obtained at a growth temperature of 23 degreesC. X-ray diffraction shows that the full width at half maximum (FWHM) of (0 0 2) ZnO, located at 34.42degrees, is approximately 0.26degrees. A pronounced exciton absorption peak is observed in the absorption spectrum. The photoluminescence (PL) spectra show a strong ultraviolet (UV) band emission approximately 3.26 eV with a weak emission related to deep-level defects, implying that the ZnO thin films are nearly stoichiometric. The FWHMs of the PL spectra become narrower with increasing growth temperature. The origin of the UV band is from free exciton recombination, testified by the temperature dependent PL spectra in the range of 81-581 K