Six ZnO thin films were grown under different oxygen flow rates by electrochemical deposition onto commercial indium tin oxide substrates. X-ray diffraction (XRD), optical absorption, and photoluminescence (PL) measurements were performed on all films. XRD measurements showed that films are highly (0002) c-axis oriented. It has been observed that the growth rates of the films are highly dependent on the oxygen flow rates. High growth rate is obtained for the midoxygen flow rates in the cell. Calculated crystallite size values have an increasing trend as the oxygen flow rate increases. Absorption measurements have revealed that the band gap energy of ZnO thin films is about 3.4 eV. PL measurements showed that two emissions are observed in all films: free exciton emission at about 3.37 eV and so-called blue emission at 2.66 eV in ZnO. Relatively low dose (5 x 10(12) e(-)/cm(2)) and high-energy electron-irradiation (HEEI) (12 MeV) experiments were performed on all films. Their effects on the optical and structural characteristics are discussed. In addition, an annealing process was applied to understand the effect on the recovery of the HEEI-induced defects. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3222865]